Correct Answer: Using knowledge from one task for another task
Explanation:
Transfer learning reuses knowledge learned from a source task or dataset for a related target task.
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2Why is transfer learning commonly used for image classification?
Transfer learning
Easy
A.It requires fewer labeled training images
B.It removes the need for an output layer
C.It guarantees perfect classification accuracy
D.It prevents images from having different sizes
Correct Answer: It requires fewer labeled training images
Explanation:
A pretrained model already contains useful visual features, so the target task often needs less labeled data.
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3What is the main feature of ResNet architectures?
ResNet
Easy
A.A complete absence of pooling layers
B.Only one convolutional layer
C.Training without labeled examples
D.Shortcut connections between layers
Correct Answer: Shortcut connections between layers
Explanation:
ResNet uses shortcut, or skip, connections that help information and gradients pass through deep networks.
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4What problem do residual connections in ResNet help address?
ResNet
Easy
A.Difficulty training very deep networks
B.Missing class names in datasets
C.Excessive image brightness
D.Lack of image file formats
Correct Answer: Difficulty training very deep networks
Explanation:
Residual connections help reduce optimization difficulties such as vanishing gradients in deep models.
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5What is a key idea behind EfficientNet?
EfficientNet
Easy
A.Using only fully connected layers
B.Training every model with one fixed image size
C.Replacing images with numerical labels
D.Scaling depth, width, and resolution together
Correct Answer: Scaling depth, width, and resolution together
Explanation:
EfficientNet uses compound scaling to balance network depth, width, and input resolution.
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6EfficientNet models are designed mainly to improve which balance?
EfficientNet
Easy
A.Labels and file compression
B.Accuracy and computational efficiency
C.Batch size and class names
D.Color and image brightness
Correct Answer: Accuracy and computational efficiency
Explanation:
EfficientNet aims to achieve strong accuracy while using computational resources efficiently.
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7What is MobileNet primarily designed for?
MobileNet
Easy
A.Processing only text-based documents
B.Training models with unlimited memory
C.Efficient use on mobile and embedded devices
D.Replacing all image preprocessing steps
Correct Answer: Efficient use on mobile and embedded devices
Explanation:
MobileNet architectures are lightweight and suitable for devices with limited memory and processing power.
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8Which operation is commonly used by MobileNet to reduce computation?
MobileNet
Easy
A.Depthwise separable convolution
B.Three-dimensional pooling only
C.Unrestricted fully connected layers
D.Repeated image enlargement
Correct Answer: Depthwise separable convolution
Explanation:
MobileNet uses depthwise separable convolutions to reduce the number of operations compared with standard convolutions.
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9In feature extraction, what is usually done with the pretrained convolutional layers?
Feature extraction
Easy
A.Their layers are randomly removed
B.Their weights are deleted
C.Their inputs are replaced with labels
D.Their weights are kept fixed
Correct Answer: Their weights are kept fixed
Explanation:
Feature extraction commonly keeps pretrained layers frozen while using them to produce features for a new classifier.
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10What do early convolutional layers often learn from images?
Feature extraction
Easy
A.Database connection rules
B.Final class names only
C.Edges and simple textures
D.Complete sentences
Correct Answer: Edges and simple textures
Explanation:
Early layers generally learn basic visual patterns such as edges, colors, and simple textures.
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11When using a pretrained model as a feature extractor, which part is commonly replaced?
Feature extraction
Easy
A.The final classification layer
B.Every convolutional filter
C.The image file extension
D.The training dataset format
Correct Answer: The final classification layer
Explanation:
The final layer is replaced so that its number of outputs matches the classes in the new task.
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12What does fine-tuning mean in transfer learning?
Fine-tuning
Easy
A.Updating some pretrained weights on new data
B.Freezing the entire neural network permanently
C.Using a model without any training
D.Changing image labels without changing model weights
Correct Answer: Updating some pretrained weights on new data
Explanation:
Fine-tuning adapts a pretrained model by continuing training on the target dataset.
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13Fine-tuning is often useful when the target dataset is:
Fine-tuning
Easy
A.Related but different from the pretraining dataset
B.Completely empty of images
C.Made only of numerical formulas
D.Identical to the model architecture
Correct Answer: Related but different from the pretraining dataset
Explanation:
Fine-tuning helps adapt useful pretrained features to a related target domain or task.
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14What does it mean to freeze a neural network layer?
Managing freezing and unfreezing of layers
Easy
A.Its filters are converted into labels
B.Its weights are not updated during training
C.Its input images are permanently resized
D.Its outputs are always set to zero
Correct Answer: Its weights are not updated during training
Explanation:
A frozen layer still performs computations, but its parameters are kept unchanged during optimization.
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15Why are pretrained layers often frozen at the beginning of training?
Managing freezing and unfreezing of layers
Easy
A.To remove the need for a loss function
B.To make every layer randomly initialized
C.To increase the number of target classes
D.To preserve useful learned features
Correct Answer: To preserve useful learned features
Explanation:
Freezing protects the pretrained representations while the new task-specific layers begin learning.
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16During gradual fine-tuning, what is commonly done after training the new classifier?
Managing freezing and unfreezing of layers
Easy
A.The model output is changed to audio
B.Some earlier layers are unfrozen
C.All input images are discarded
D.The loss function is removed
Correct Answer: Some earlier layers are unfrozen
Explanation:
Unfreezing selected layers allows the model to adapt deeper pretrained features to the target dataset.
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17What is a layer-wise learning rate strategy?
Applying layer-wise learning rates
Easy
A.Assigning one label to every layer
B.Using different learning rates for different layers
C.Using one batch for every layer
D.Changing the image size after every layer
Correct Answer: Using different learning rates for different layers
Explanation:
Layer-wise learning rates assign separate update sizes to different parts of the network.
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18Which learning rate is commonly used for newly added classification layers?
Applying layer-wise learning rates
Easy
A.A smaller rate than every frozen layer
B.A rate that never changes model weights
C.A permanently zero learning rate
D.A relatively larger learning rate
Correct Answer: A relatively larger learning rate
Explanation:
New layers usually need larger updates because their weights are not pretrained for the target task.
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19What is domain adaptation used for?
Domain adaptation and dataset
Easy
A.Removing all differences between image classes
B.Converting a classification task into file storage
C.Adapting a model to a different data distribution
D.Increasing the number of network parameters automatically
Correct Answer: Adapting a model to a different data distribution
Explanation:
Domain adaptation helps a model trained in one domain perform better in a related but different domain.
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20What is the target dataset in transfer learning?
Domain adaptation and dataset
Easy
A.A dataset that has no relationship to the task
B.A dataset containing model source code
C.The dataset used for the new task
D.The dataset used only to initialize random numbers
Correct Answer: The dataset used for the new task
Explanation:
The target dataset contains examples from the task or domain where the pretrained model will be applied.
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21A team has 2,000 labeled images of industrial defects and a model pretrained on ImageNet. What is the most appropriate initial transfer-learning strategy?
Transfer learning
Medium
A.Replace all convolutional layers with fully connected layers
B.Freeze the classifier and retrain only the earliest convolution
C.Train the entire network from randomly initialized weights
D.Freeze the backbone and train a new task-specific classifier
Correct Answer: Freeze the backbone and train a new task-specific classifier
Explanation:
With a small labeled dataset, using the pretrained backbone as a fixed feature extractor reduces overfitting while adapting the classifier to the new task.
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22Transfer learning from ImageNet is likely to provide the smallest benefit for which target task?
Transfer learning
Medium
A.Classifying patterns in radar measurements that differ substantially from natural images
B.Identifying species in wildlife photographs
C.Classifying common household objects
D.Recognizing vehicles in street images
Correct Answer: Classifying patterns in radar measurements that differ substantially from natural images
Explanation:
ImageNet features transfer less effectively when the target data has visual statistics and structures that differ substantially from natural RGB images.
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23A 50-layer plain CNN trains poorly, while a ResNet-50 trains successfully on the same dataset. Which ResNet mechanism most directly explains the improvement?
ResNet
Medium
A.Residual connections provide shorter paths for gradient flow
B.Max pooling prevents every vanishing-gradient problem
C.Dropout is automatically added after each convolution
D.Residual blocks remove the need for nonlinear activations
Correct Answer: Residual connections provide shorter paths for gradient flow
Explanation:
Skip connections let gradients flow through identity paths, making very deep networks easier to optimize.
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24In a ResNet block, the residual branch produces and the shortcut carries . When their shapes match, what is the block output before the final activation?
ResNet
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
A standard residual block adds the learned residual mapping to the shortcut input, giving .
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25A practitioner wants to scale an EfficientNet model while preserving its core scaling principle. Which change best follows compound scaling?
EfficientNet
Medium
A.Increase width and remove all resolution scaling to keep the model's spatial dimensions unchanged
B.Increase only depth while keeping width and resolution fixed
C.Increase depth, width, and input resolution in a balanced way
D.Increase only input resolution until GPU memory is exhausted
Correct Answer: Increase depth, width, and input resolution in a balanced way
Explanation:
EfficientNet compound scaling jointly adjusts network depth, width, and image resolution using coordinated scaling coefficients.
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26When replacing EfficientNet-B0 with a larger EfficientNet variant for transfer learning, what trade-off should be expected?
EfficientNet
Medium
A.Identical accuracy with lower computation and memory use
B.Fewer parameters because every larger variant uses stronger pooling
C.Potentially better accuracy with greater computation and memory use
D.No change in inference latency because compound scaling affects training only
Correct Answer: Potentially better accuracy with greater computation and memory use
Explanation:
Larger EfficientNet variants generally offer more representational capacity, but they require more computation and memory.
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27Why is MobileNet commonly selected for an image-classification application running on a mobile device?
MobileNet
Medium
A.Every convolution operates only on one-pixel input images
B.Depthwise separable convolutions reduce computation and parameters
D.Residual additions eliminate the need to store feature maps
Correct Answer: Depthwise separable convolutions reduce computation and parameters
Explanation:
MobileNet uses depthwise and pointwise convolutions to perform spatial and channel mixing more efficiently than standard convolutions.
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28A MobileNet model uses a width multiplier . What is the primary effect of decreasing ?
MobileNet
Medium
A.It reduces channel counts and computational cost
B.It freezes a larger fraction of pretrained layers
C.It converts depthwise convolutions into standard convolutions with additional trainable kernels
D.It increases image resolution and receptive-field size
Correct Answer: It reduces channel counts and computational cost
Explanation:
The width multiplier scales the number of channels, so a smaller creates a narrower and less expensive network.
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29A pretrained CNN is used only to compute embeddings, which are then supplied to a newly trained linear classifier. Which layer output is usually the most suitable embedding?
Feature extraction
Medium
A.The raw RGB image before normalization
B.The loss value computed after each training batch
C.The original classifier's class-probability vector
D.The final pooled feature vector before the original classifier
Correct Answer: The final pooled feature vector before the original classifier
Explanation:
The pooled vector before the original classification head contains high-level visual features without being restricted to the original class predictions.
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30A frozen pretrained backbone is used for feature extraction, but the new classifier overfits. Which intervention most directly addresses the problem without modifying backbone weights?
Feature extraction
Medium
A.Add regularization and augmentation while training the classifier
B.Unfreeze every backbone layer and greatly increase its learning rate
C.Remove the validation set to provide more classifier training samples
D.Cache each training feature multiple times and treat the copies as independently labeled examples
Correct Answer: Add regularization and augmentation while training the classifier
Explanation:
Regularization and meaningful data augmentation can improve generalization while keeping the pretrained backbone frozen.
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31After training a new classification head, a practitioner unfreezes part of the pretrained backbone. Which learning-rate change is generally appropriate?
Fine-tuning
Medium
A.Use the largest stable learning rate for all layers
B.Set the backbone learning rate permanently to zero
C.Use a smaller learning rate for the unfrozen backbone
D.Increase the learning rate whenever validation loss rises
Correct Answer: Use a smaller learning rate for the unfrozen backbone
Explanation:
A smaller learning rate updates pretrained features gradually and reduces the risk of destroying useful representations.
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32During fine-tuning, training accuracy rises while validation accuracy falls after several epochs. What is the most appropriate response?
Fine-tuning
Medium
A.Increase model size without changing the training setup
B.Continue training until both accuracies reach 100%
C.Apply early stopping and strengthen regularization
D.Evaluate only on the training set because pretrained models do not require validation
Correct Answer: Apply early stopping and strengthen regularization
Explanation:
The widening train-validation gap indicates overfitting, which can be reduced through early stopping, augmentation, weight decay, or dropout.
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33For a small target dataset similar to ImageNet, which staged training procedure is generally most appropriate?
Managing freezing and unfreezing of layers
Medium
A.Train the new head, then unfreeze later blocks gradually
B.Unfreeze the entire network before training the new head
C.Train only the earliest convolution and discard later blocks
D.Alternate frozen and unfrozen states after every individual batch throughout training
Correct Answer: Train the new head, then unfreeze later blocks gradually
Explanation:
Training the head first stabilizes task-specific predictions, while gradual unfreezing allows controlled adaptation of higher-level features.
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34Why are the final backbone blocks usually unfrozen before the earliest blocks?
Managing freezing and unfreezing of layers
Medium
A.Earlier blocks contain no trainable parameters
B.Later blocks always require less GPU memory
C.Later blocks contain more task-specific semantic features
D.Earlier blocks produce class probabilities rather than visual features
Correct Answer: Later blocks contain more task-specific semantic features
Explanation:
Early layers commonly learn general edges and textures, while later layers encode semantic patterns that often need more adaptation to the target task.
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35A frozen backbone contains Batch Normalization layers. The validation performance becomes unstable when these layers continue updating their running statistics on very small batches. What should be tried?
Managing freezing and unfreezing of layers
Medium
A.Increase the classifier learning rate after every batch
B.Replace running means with randomly sampled values during each validation pass
C.Keep the Batch Normalization layers in evaluation mode
D.Delete all normalization layers from the pretrained network
Correct Answer: Keep the Batch Normalization layers in evaluation mode
Explanation:
Evaluation mode preserves the pretrained running statistics, avoiding noisy updates caused by small target-domain batches.
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36A model is divided into an early backbone, a late backbone, and a new classifier. Which learning-rate assignment best matches discriminative fine-tuning?
Applying layer-wise learning rates
Medium
A., , and , respectively
B., , and , respectively
C., , and , respectively
D., , and , respectively
Correct Answer: , , and , respectively
Explanation:
Earlier pretrained layers receive smaller updates, later layers adapt more, and the randomly initialized classifier uses the largest learning rate.
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37Why can layer-wise learning rates reduce catastrophic forgetting during transfer learning?
Applying layer-wise learning rates
Medium
A.They limit changes to general features in early layers
B.They guarantee that the target dataset has balanced classes
C.They prevent the classifier from receiving any gradients
D.They force all layers to converge to identical parameter values after each optimization step
Correct Answer: They limit changes to general features in early layers
Explanation:
Small learning rates in early layers preserve broadly useful pretrained features while larger rates allow task-specific layers to adapt.
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38A classifier is trained on studio product photos but deployed on dim warehouse-camera images. Which change most directly reduces this domain shift?
Domain adaptation and dataset
Medium
A.Shuffle the studio training set using a different random seed
B.Increase the number of source-domain output classes
C.Add more studio photos with the same lighting
D.Fine-tune using labeled warehouse-camera images
Correct Answer: Fine-tune using labeled warehouse-camera images
Explanation:
Target-domain examples expose the model to the lighting, noise, and viewpoint conditions it will encounter during deployment.
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39Only unlabeled target-domain images are available. Which technique can still help align source and target representations?
Domain adaptation and dataset
Medium
A.Assigning every target image to the most frequent source class and treating those assignments as verified ground truth
B.Supervised fine-tuning using invented target labels
C.Training only on source labels without using target images
D.Adversarial domain adaptation with a domain discriminator
Correct Answer: Adversarial domain adaptation with a domain discriminator
Explanation:
A domain discriminator can encourage features that are useful for the task but less informative about whether an image came from the source or target domain.
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40A medical-image dataset contains multiple scans from each patient. Which split best avoids leakage when evaluating a transfer-learned model?
Domain adaptation and dataset
Medium
A.Use the same patient scans for training and testing but apply different image normalization methods
B.Randomly split individual scans across all dataset splits
C.Assign all scans from a patient to only one split
D.Place augmented scans in validation and originals in training
Correct Answer: Assign all scans from a patient to only one split
Explanation:
Patient-level splitting prevents closely related scans from the same person appearing in both training and evaluation data, producing a more reliable estimate of generalization.
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41A CNN pretrained on ImageNet is transferred to a medical-image dataset with only 800 labeled examples. The target images are grayscale, but their low-level edge statistics resemble natural images. Which initialization strategy is most defensible?
Transfer learning
Hard
A.Replace every convolutional filter with random weights before classifier training
B.Replicate the grayscale channel three times and retain pretrained convolutional weights
C.Convert filters to grayscale and train all layers with the same large learning rate
D.Initialize the first layer randomly and retain only the pretrained classifier weights
Correct Answer: Replicate the grayscale channel three times and retain pretrained convolutional weights
Explanation:
Channel replication preserves the pretrained input interface and allows useful low-level features to transfer. With limited data, retaining these features generally reduces overfitting.
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42In a pretrained ResNet block, the identity shortcut has dimension while the residual branch outputs channels and uses stride 2. Which modification preserves the residual-addition operation?
ResNet
Hard
A.Remove the shortcut and double the residual branch activation width
B.Add zero padding to the identity tensor without changing its spatial size
C.Use a projection with stride 2 on the identity branch
D.Average the residual channels into channels before addition
Correct Answer: Use a projection with stride 2 on the identity branch
Explanation:
The projection must simultaneously match spatial resolution and channel count. A convolution with stride 2 maps the identity from channels to channels.
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43EfficientNet scales network depth, width, and input resolution using a compound coefficient. If compute is approximately proportional to , which scaling choice best preserves balanced growth when increasing model capacity?
EfficientNet
Hard
A.Increase only width because channel expansion dominates representational capacity
B.Increase depth, width, and resolution by unrelated manually selected factors
C.Increase resolution first and keep depth and width fixed for stability
D.Increase all three dimensions under a shared compound scaling constraint
Correct Answer: Increase all three dimensions under a shared compound scaling constraint
Explanation:
Compound scaling coordinates depth, width, and resolution so that capacity and compute grow in a controlled way. Scaling one dimension alone can create an inefficient or poorly balanced model.
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44For an input feature map of size and a depthwise-separable convolution producing output channels with kernel size , what is the approximate parameter reduction relative to a standard convolution?
MobileNet
Hard
A.From to
B.From to
C.From to
D.From to
Correct Answer: From to
Explanation:
Depthwise convolution uses parameters, followed by pointwise convolution using . A standard convolution uses parameters.
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45A frozen backbone produces features that separate training classes well, but target validation accuracy remains poor after replacing the classifier. Which observation most strongly suggests that the fixed representation is unsuitable for the target task?
Feature extraction
Hard
A.The backbone contains more parameters than the newly initialized classifier
B.The target classifier uses fewer output units than the source classifier
C.The classifier loss decreases while validation errors remain structured by target subdomain
D.The optimizer reports a lower learning rate for the classifier than for the backbone
Correct Answer: The classifier loss decreases while validation errors remain structured by target subdomain
Explanation:
Structured errors across target subdomains indicate that discriminative information is not adequately represented by the frozen features. A trainable classifier cannot recover information discarded by the backbone.
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46A pretrained model reaches high training accuracy immediately after unfreezing all layers, but target validation accuracy falls and feature norms grow rapidly. Which intervention is most appropriate first?
Fine-tuning
Hard
A.Freeze only the classifier and increase augmentation strength afterward
B.Increase the learning rate to escape the pretrained parameter basin
C.Use a smaller backbone learning rate with stronger regularization
D.Reinitialize the backbone and train it from scratch on the target set
Correct Answer: Use a smaller backbone learning rate with stronger regularization
Explanation:
Rapid memorization and feature drift are consistent with catastrophic forgetting and overfitting. A smaller backbone learning rate, combined with regularization, preserves useful pretrained structure while allowing adaptation.
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47During staged fine-tuning, the backbone is frozen but contains BatchNorm layers. The target dataset has a different intensity distribution and is small. Which configuration is generally safest?
Managing freezing and unfreezing of layers
Hard
A.Replace BatchNorm with dropout and unfreeze every convolutional layer
B.Remove all BatchNorm layers before transferring the pretrained backbone
C.Keep BatchNorm statistics frozen while training only the new classifier
D.Update BatchNorm statistics on every target batch regardless of batch size
Correct Answer: Keep BatchNorm statistics frozen while training only the new classifier
Explanation:
Small target batches produce noisy BatchNorm estimates, and updating statistics can destabilize a frozen representation. Frozen statistics provide more predictable behavior during classifier-only training.
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48A three-stage backbone uses learning rates , , and from the earliest to latest stage, while the new classifier uses . What principle does this schedule encode?
Applying layer-wise learning rates
Hard
A.Earlier features receive larger updates because they have higher generality
B.The classifier is protected from overfitting by using the largest learning rate
C.Later features and the classifier adapt more rapidly to target semantics
D.Every stage receives the same effective update after normalization
Correct Answer: Later features and the classifier adapt more rapidly to target semantics
Explanation:
Early layers usually contain more transferable features, whereas later layers are more task-specific. Smaller learning rates protect early representations and larger rates accelerate target-specific adaptation.
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49A source model classifies daytime street images, while the target dataset contains nighttime images with identical labels. Unlabeled target data are abundant. Which method directly addresses the domain shift without requiring target labels?
Domain adaptation and dataset
Hard
A.Discard nighttime images because their labels cannot be verified
B.Align source and target feature distributions with an unsupervised adaptation loss
C.Use random labels for target images to balance the training batches
D.Train a larger classifier using only the labeled source images
Correct Answer: Align source and target feature distributions with an unsupervised adaptation loss
Explanation:
Unsupervised domain adaptation uses unlabeled target data to reduce distribution mismatch, often by aligning intermediate feature distributions while preserving source supervision.
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50A target dataset has the same visual domain as the pretraining data but a highly different label taxonomy. Which transfer strategy best reduces harmful source-task bias?
Transfer learning
Hard
A.Reuse the entire source classifier and freeze the complete network
B.Reuse the backbone, replace the classifier, and tune upper layers cautiously
C.Train only the source classifier until its accuracy stops improving
D.Copy source logits directly into the target labels without recalibration
Correct Answer: Reuse the backbone, replace the classifier, and tune upper layers cautiously
Explanation:
The visual domain supports backbone reuse, but the different taxonomy makes the source classifier inappropriate. Replacing it and adapting upper layers allows semantic features to shift toward the target labels.
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51Why can a ResNet often be fine-tuned more deeply than a plain network of comparable depth, even when the target dataset is small?
ResNet
Hard
A.Residual branches eliminate the need for normalization during adaptation
B.Shortcut connections guarantee that target-domain features are linearly separable
C.Residual shortcuts make every layer independent of the loss function
D.Identity paths improve gradient propagation and preserve pretrained representations
The identity path gives gradients a direct route and lets the network retain useful features while residual branches learn corrections. It does not guarantee separability or eliminate normalization.
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52When transferring an EfficientNet model to a target dataset whose objects occupy much smaller image regions than in pretraining, which change is most likely to help before substantially increasing model width?
EfficientNet
Hard
A.Replace depthwise convolutions with fully connected layers at every stage
B.Remove squeeze-and-excitation modules to prevent channel recalibration
C.Increase input resolution while preserving the architecture's scaling assumptions
D.Reduce input resolution so the object occupies fewer feature-map cells
Correct Answer: Increase input resolution while preserving the architecture's scaling assumptions
Explanation:
Higher input resolution can retain more spatial detail for small objects. EfficientNet's design couples resolution with depth and width, so changes should remain consistent with the model's scaling configuration.
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53A MobileNet-based classifier must run under a strict latency budget. Validation accuracy improves after increasing width, but measured latency exceeds the budget. Which adjustment is most principled?
MobileNet
Hard
A.Reduce the width multiplier and evaluate accuracy at the deployment resolution
B.Increase width further and compensate with heavier quantization later
C.Replace depthwise convolutions with standard convolutions for better hardware use
D.Add dense layers because parameter count alone determines inference latency
Correct Answer: Reduce the width multiplier and evaluate accuracy at the deployment resolution
Explanation:
The width multiplier directly controls channel count and computational cost. Deployment latency depends on hardware and resolution, so the adjusted model must be benchmarked under realistic conditions.
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54A frozen backbone is used with global average pooling. The target classes differ mainly by precise spatial arrangement rather than overall texture. What limitation should be expected?
Feature extraction
Hard
A.Global pooling makes the feature dimension dependent on image width
B.Global pooling always increases sensitivity to object translation errors
C.Global pooling prevents gradients from reaching the classifier parameters
D.Global pooling may discard spatial information needed to distinguish arrangements
Correct Answer: Global pooling may discard spatial information needed to distinguish arrangements
Explanation:
Global average pooling summarizes each channel across spatial positions. This improves size flexibility but can remove layout information required by fine-grained spatial distinctions.
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55A target dataset contains severe class imbalance. During fine-tuning, overall accuracy rises while minority-class recall collapses. Which evaluation and optimization change is most appropriate?
Fine-tuning
Hard
A.Reduce augmentation because minority examples should remain visually identical
B.Use balanced metrics and class-aware loss or sampling during adaptation
C.Use accuracy alone because it reflects the deployment class frequencies
D.Freeze the classifier and optimize only the backbone with unweighted loss
Correct Answer: Use balanced metrics and class-aware loss or sampling during adaptation
Explanation:
Overall accuracy can hide minority-class failure. Balanced metrics expose the issue, while class weighting or class-aware sampling changes the training signal toward underrepresented classes.
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56After unfreezing a new block, its gradients are nonzero but its weights appear unchanged during training. Which implementation issue is most likely?
Managing freezing and unfreezing of layers
Hard
A.The classifier has a larger output dimension than the backbone
B.The input images were normalized using source statistics
C.The residual block contains an identity shortcut
D.The block is absent from the optimizer parameter groups
Correct Answer: The block is absent from the optimizer parameter groups
Explanation:
A parameter can require gradients yet remain unchanged if the optimizer does not manage it. After changing requires_grad, the parameter groups must be updated or the optimizer recreated.
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57Two layers have gradients with similar magnitudes, but the earlier layer has much larger pretrained weights and is more transferable. Why can assigning it a smaller learning rate still be justified?
Applying layer-wise learning rates
Hard
A.Layer-wise rates remove the need to monitor validation performance
B.Learning rates determine only gradient direction, not parameter displacement
C.Smaller rates limit relative parameter drift and protect established features
D.Smaller rates guarantee identical updates across layers with different norms
Correct Answer: Smaller rates limit relative parameter drift and protect established features
Explanation:
The practical effect of an update depends on its size relative to the parameter values. Smaller rates for early layers reduce disruptive changes to transferable representations.
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58A target validation set was collected from the same camera and locations as the training set, while deployment uses unseen cameras. Fine-tuning improves validation accuracy but deployment performance decreases. What is the primary diagnosis?
Domain adaptation and dataset
Hard
A.The source dataset must be discarded because deployment has unseen cameras
B.The target classifier requires more output classes than the deployment system
C.The backbone has become too shallow to represent camera-specific features
D.The model has overfit the validation distribution and the evaluation is not representative
Correct Answer: The model has overfit the validation distribution and the evaluation is not representative
Explanation:
Camera and location overlap can make validation overly optimistic. Deployment performance reveals a camera-domain shift, so evaluation should use held-out cameras or a domain-balanced protocol.
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59A target dataset is larger than the source pretraining dataset but differs substantially in sensor modality and image formation. Which conclusion is most defensible?
Transfer learning
Hard
A.The target dataset size alone guarantees that transfer will improve accuracy
B.The pretrained model should always be frozen because modality changes are irreversible
C.Source pretraining is useless whenever the target dataset has more examples
D.Transfer may still help, but modality mismatch should be tested against strong baselines
Correct Answer: Transfer may still help, but modality mismatch should be tested against strong baselines
Explanation:
Dataset size does not determine transfer quality by itself. Pretrained features may provide useful structure, but severe modality mismatch makes scratch training and partial-transfer baselines important.
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60A fine-tuned model performs well on clean target images but fails under a mild illumination change that is common in deployment. Which response best targets the failure mode?
Fine-tuning
Hard
A.Remove validation images with illumination changes to stabilize the metric
B.Increase classifier depth without changing the training distribution
C.Use augmentation or domain-relevant normalization that represents illumination variation
D.Freeze all layers permanently so illumination cannot affect learned features
Correct Answer: Use augmentation or domain-relevant normalization that represents illumination variation
Explanation:
The failure indicates insufficient robustness to a known deployment variation. Training with representative illumination changes encourages invariant features and makes validation better reflect operational conditions.
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