A.A graph with multiple edges between the same pair of vertices.
B.A graph containing loops but no multiple edges.
C.A graph with no loops and no multiple edges.
D.A graph where edges have direction.
Correct Answer: A graph with no loops and no multiple edges.
Explanation:A simple graph is defined as an undirected graph that does not contain any loops (edges connecting a vertex to itself) or multiple edges (more than one edge connecting the same pair of vertices).
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2According to the Handshaking Theorem, the sum of degrees of all vertices in an undirected graph is equal to:
A.The number of edges.
B.Twice the number of edges.
C.The number of vertices squared.
D.Half the number of edges.
Correct Answer: Twice the number of edges.
Explanation:The Handshaking Theorem states that , because every edge connects two vertices and contributes 1 to the degree of each, totaling 2 per edge.
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3In any undirected graph, the number of vertices with an odd degree is always:
A.Odd
B.Even
C.Prime
D.Zero
Correct Answer: Even
Explanation:This is a corollary of the Handshaking Theorem. Since the sum of all degrees is even (), the sum of the degrees of odd-degree vertices must be even. For a sum of odd integers to be even, there must be an even number of such integers.
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4What is the maximum number of edges in a simple undirected graph with vertices?
A.
B.
C.
D.
Correct Answer:
Explanation:In a simple graph with vertices, every vertex can connect to every other vertex exactly once. This is equivalent to choosing 2 vertices from , which is .
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5A vertex with a degree of 0 is called a(n):
A.Pendant vertex
B.Isolated vertex
C.Cut vertex
D.Root vertex
Correct Answer: Isolated vertex
Explanation:An isolated vertex is a vertex that is not adjacent to any other vertices, meaning its degree is 0.
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6A vertex with a degree of 1 is called a(n):
A.Isolated vertex
B.Pendant vertex
C.Internal vertex
D.Universal vertex
Correct Answer: Pendant vertex
Explanation:A pendant vertex (or leaf node) is a vertex connected to exactly one edge, giving it a degree of 1.
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7How many edges does the Complete Graph have?
A.5
B.10
C.20
D.25
Correct Answer: 10
Explanation:A complete graph has edges. For , edges = .
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8Which of the following statements is true for a Complete Bipartite Graph ?
A.The vertex set is partitioned into two sets of size and , and every vertex in one set is connected to every vertex in the other.
B.Every vertex is connected to every other vertex in the graph.
C.It is a graph consisting of a single cycle of length .
D.It is a regular graph of degree .
Correct Answer: The vertex set is partitioned into two sets of size and , and every vertex in one set is connected to every vertex in the other.
Explanation:This is the definition of . Edges only exist between the two disjoint sets, and all possible edges between these sets exist.
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9How many edges are there in the Complete Bipartite Graph ?
A.7
B.12
C.24
D.6
Correct Answer: 12
Explanation:The number of edges in a complete bipartite graph is . Here, .
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10A graph in which every vertex has the same degree is called a:
A.Complete graph
B.Bipartite graph
C.-regular graph
D.Connected graph
Correct Answer: -regular graph
Explanation:A regular graph is a graph where each vertex has the same number of neighbors. If that number is , it is called a -regular graph.
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11The Cycle Graph (for ) is a regular graph of degree:
A.
B.
C.2
D.3
Correct Answer: 2
Explanation:In a cycle graph , every vertex is connected to exactly two other vertices (the previous one and the next one in the cycle). Thus, it is 2-regular.
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12How many vertices and edges does the Wheel Graph have?
A. vertices and edges
B. vertices and edges
C. vertices and edges
D. vertices and edges
Correct Answer: vertices and edges
Explanation:A wheel graph is formed by adding a single vertex to a cycle and connecting it to all vertices of the cycle. Total vertices = . Total edges = (from cycle) + (spokes) = .
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13The n-cube (or hypercube) graph has how many vertices?
A.
B.
C.
D.
Correct Answer:
Explanation:The graph represents the vertices and edges of an -dimensional hypercube. The vertices can be represented by bit strings of length , so there are vertices.
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14What is the degree of every vertex in the cube graph ?
A.2
B.3
C.4
D.8
Correct Answer: 3
Explanation: is an -regular graph. Therefore, in , every vertex has a degree of 3.
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15A graph is bipartite if and only if:
A.It has no odd cycles.
B.It has no even cycles.
C.It is a complete graph.
D.It is connected.
Correct Answer: It has no odd cycles.
Explanation:A well-known theorem states that a graph is bipartite if and only if it contains no cycles of odd length. This allows the vertices to be colored with 2 colors such that no adjacent vertices share a color.
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16What is the size of the Adjacency Matrix for a graph with vertices?
A.
B.
C.
D.
Correct Answer:
Explanation:An adjacency matrix is a square matrix where rows and columns represent vertices. Thus, for vertices, the size is .
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17In an adjacency matrix for an undirected simple graph, what does signify?
A.There is a path of length 1 between vertex and vertex .
B.Vertex and vertex are the same.
C.There are multiple edges between and .
D.There is no connection between and .
Correct Answer: There is a path of length 1 between vertex and vertex .
Explanation:If , it means there is an edge connecting vertex and vertex (an edge is a path of length 1).
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18For an undirected graph, the Adjacency Matrix is always:
A.Skew-symmetric
B.Symmetric
C.Identity matrix
D.Lower triangular
Correct Answer: Symmetric
Explanation:In an undirected graph, if vertex is connected to , then is connected to . Thus, , making the matrix symmetric.
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19Let be the adjacency matrix of a simple graph. The entry in the position of (matrix raised to power ) represents:
A.The shortest distance between and .
B.The number of paths of length exactly between and .
C.1 if there is a path of length , 0 otherwise.
D.The number of edges between and multiplied by .
Correct Answer: The number of paths of length exactly between and .
Explanation:A property of the powers of the adjacency matrix is that the element equals the number of distinct walks (paths if vertices distinct) of length from vertex to vertex .
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20The Incidence Matrix of an undirected graph with vertices and edges has dimensions:
A.
B.
C.
D.
Correct Answer:
Explanation:Rows represent vertices () and columns represent edges (). Thus, the dimension is .
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21In the Incidence Matrix of a simple undirected graph without loops, each column sums to:
A.0
B.1
C.2
D.The degree of the corresponding vertex
Correct Answer: 2
Explanation:Each column represents an edge. Since an edge connects exactly two vertices, there are exactly two 1s in every column (representing the two endpoints), so the sum is 2.
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22The sum of the entries in a row of the Adjacency Matrix of an undirected graph represents:
A.The number of edges in the graph.
B.The degree of vertex .
C.The number of loops at vertex .
D.Zero.
Correct Answer: The degree of vertex .
Explanation:Summing the 1s in a row counts how many vertices are adjacent to vertex , which is the definition of the degree of .
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23Two graphs and are isomorphic if:
A.They have the same number of vertices and edges.
B.They have the same degree sequence.
C.There exists a bijection between their vertex sets that preserves adjacency.
D.They can be drawn without crossing edges.
Correct Answer: There exists a bijection between their vertex sets that preserves adjacency.
Explanation:Graph isomorphism requires a one-to-one correspondence (bijection) such that is an edge in iff is an edge in .
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24Which of the following is NOT an invariant of graph isomorphism? (i.e., property preserved by isomorphism)
A.Number of vertices
B.Number of edges
C.Degree sequence
D.Labels of the vertices
Correct Answer: Labels of the vertices
Explanation:Isomorphism is about structural equivalence. The specific names or labels of the vertices do not matter and are not preserved; only the connectivity structure is.
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25A walk in a graph where all edges are distinct is called a:
A.Path
B.Trail
C.Circuit
D.Cycle
Correct Answer: Trail
Explanation:A walk is a sequence of vertices and edges. If edges are not repeated, it is a trail. If vertices are not repeated, it is a path (simple path).
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26A path that begins and ends at the same vertex is called a:
A.Cycle (or Circuit)
B.Simple Path
C.Walk
D.Tree
Correct Answer: Cycle (or Circuit)
Explanation:A closed path (starting and ending at the same vertex) is generally called a cycle or circuit depending on whether vertices or edges are repeated.
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27An undirected graph is called connected if:
A.It contains a cycle.
B.Every pair of distinct vertices has a path between them.
C.It is a complete graph.
D.Every vertex has an odd degree.
Correct Answer: Every pair of distinct vertices has a path between them.
Explanation:Connectivity implies there is a way to get from any vertex to any other vertex in the graph.
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28A vertex whose removal increases the number of connected components in a graph is called a:
Explanation:This is the standard definition of a cut vertex. Removing it disconnects a previously connected component.
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29An edge whose removal increases the number of connected components is called a:
A.Cut vertex
B.Bridge (or Cut edge)
C.Loop
D.Parallel edge
Correct Answer: Bridge (or Cut edge)
Explanation:A bridge is an edge which, if deleted, disconnects the graph.
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30In a directed graph (digraph), the in-degree of a vertex is:
A.The number of edges leaving the vertex.
B.The number of edges entering the vertex.
C.The total number of edges connected to the vertex.
D.The number of loops on the vertex.
Correct Answer: The number of edges entering the vertex.
Explanation:In a digraph, edges have direction. In-degree counts the arrows pointing into the vertex.
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31A directed graph is strongly connected if:
A.There is a path between every pair of vertices in the underlying undirected graph.
B.There is a directed path from to and from to for every pair of vertices .
C.It has no cycles.
D.Every vertex has the same in-degree and out-degree.
Correct Answer: There is a directed path from to and from to for every pair of vertices .
Explanation:Strong connectivity requires navigability in both directions between any two nodes following the edge directions.
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32For a directed graph, the sum of the in-degrees of all vertices is equal to:
A.The sum of the out-degrees.
B.The number of edges.
C.Both A and B.
D.None of the above.
Correct Answer: Both A and B.
Explanation:Every directed edge has exactly one start (out-degree contribution) and one end (in-degree contribution). Thus, .
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33Dijkstra’s Algorithm is used to find:
A.The Minimum Spanning Tree.
B.The shortest paths from a single source vertex to all other vertices.
C.The shortest path between every pair of vertices (All-pairs).
D.The topological sort of a graph.
Correct Answer: The shortest paths from a single source vertex to all other vertices.
Explanation:Dijkstra's algorithm solves the single-source shortest path problem in graphs with non-negative edge weights.
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34Dijkstra’s Algorithm cannot be used on graphs with:
A.Cycles
B.Negative edge weights
C.Directed edges
D.Weighted edges
Correct Answer: Negative edge weights
Explanation:Dijkstra's greedy approach fails if there are negative edge weights, as it assumes that extending a path always increases (or keeps constant) the cost.
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35In Dijkstra's algorithm, what represents the initial distance value for the source vertex?
A.Infinity
B.1
C.0
D.-1
Correct Answer: 0
Explanation:The distance from the source to itself is always 0. All other vertices are initialized to infinity.
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36Which data structure is most efficiently used to select the vertex with the minimum distance in Dijkstra's algorithm?
A.Stack
B.Queue
C.Priority Queue (or Min-Heap)
D.Hash Table
Correct Answer: Priority Queue (or Min-Heap)
Explanation:A priority queue allows efficient retrieval and removal of the vertex with the currently smallest tentative distance.
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37If the adjacency matrix of a graph is , what type of graph is it?
A.
B.
C. (or Path of length 2)
D.
Correct Answer: (or Path of length 2)
Explanation:Vertex 1 is connected to 2 and 3. Vertices 2 and 3 are only connected to 1 (and not each other). This is a star graph or .
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38Which of these graphs is NOT bipartite?
A.
B.
C.
D.
Correct Answer:
Explanation: is a cycle of length 3 (triangle). Since 3 is odd, the graph contains an odd cycle and cannot be bipartite.
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39How many edges are in the cycle graph ?
A.4
B.5
C.10
D.20
Correct Answer: 5
Explanation:A cycle graph always has vertices and edges.
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40In graph theory, two edges are said to be parallel or multiple if:
A.They do not intersect.
B.They are incident on the same pair of vertices.
C.They share exactly one vertex.
D.They have the same weight.
Correct Answer: They are incident on the same pair of vertices.
Explanation:Parallel edges connect the exact same two endpoints.
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41Which of the following is true about the complement of a complete graph ?
A.It is also a complete graph.
B.It is a connected graph.
C.It is a null graph (graph with no edges).
D.It is a cycle graph.
Correct Answer: It is a null graph (graph with no edges).
Explanation:The complement of a graph contains all edges that are NOT in the original graph. Since has all possible edges, its complement has 0 edges.
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42If a graph has vertices and edges and is connected, what is the minimum value for ?
A.
B.
C.
D.
Correct Answer:
Explanation:The minimum number of edges required to connect vertices is a tree structure, which has edges.
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43The degree sequence of a graph is 4, 4, 4, 2, 2. What is the sum of the degrees?
A.12
B.16
C.10
D.20
Correct Answer: 16
Explanation:.
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44Based on the degree sequence 4, 4, 4, 2, 2, how many edges does the graph have?
A.16
B.8
C.32
D.4
Correct Answer: 8
Explanation:By the Handshaking Theorem, . Sum is 16, so .
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45What is a Sub-graph?
A.A graph with half the vertices of the original.
B.A graph where and .
C.The complement of a graph.
D.A graph that is isomorphic to the original.
Correct Answer: A graph where and .
Explanation:A subgraph is formed by a subset of the vertices and a subset of the edges of the original graph (where edges must connect vertices in the subset).
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46Which of the following graphs is Regular?
A.
B.
C.
D.Path graph
Correct Answer:
Explanation: is a complete graph where every vertex has degree 3. has degrees 3 and 2. has center degree 4 and rim degree 3. has degrees 1 and 2.
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47Consider a directed graph. If there is a path from vertex to vertex , is reachable from ?
A.Yes
B.No
C.Only if the graph is undirected
D.Only if the path is length 1
Correct Answer: Yes
Explanation:Reachability is defined by the existence of a path.
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48If a simple connected planar graph has vertices, edges, and faces, Euler's formula states:
A.
B.
C.
D.
Correct Answer:
Explanation:This is the standard Euler's Formula for connected planar graphs.
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49What is the Out-degree of vertex A in the graph with edges: , , ?
A.1
B.2
C.3
D.0
Correct Answer: 2
Explanation:There are two edges starting from A ( and ).
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50Which graph represents the 1-skeleton of a tetrahedron?
A.
B.
C.
D.
Correct Answer:
Explanation:A tetrahedron has 4 vertices, and every vertex is connected to every other vertex by an edge. This structure is isomorphic to the complete graph .