Which of the following graphs is isomorphic to
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GATE CSE 2012 · Q26
Time

Select one answerSingle correct
Solution
Official answer: B)
Discrete MathematicsTo check graph isomorphism between the given graph and the options, we examine the structural invariants:
Vertex and Edge Count:
The given graph has vertices and edges.
Degree Sequence:
The given graph consists of a -cycle with one vertex connected to pendant vertices (degree ).
The degrees of the vertices are: one vertex of degree , four vertices of degree (forming a -cycle with the degree- vertex), and two vertices of degree .
Degree sequence: .
Analyzing Option (B):
Option (B) contains vertices and edges.
The central vertex has degree .
It is adjacent to two vertices of degree (pendants) and two vertices of degree that are part of a -cycle.
Hence, graph (B) is isomorphic to the given graph.
Try the question first, then check your work.
Examiner trap
Check graph invariants such as vertex degrees, cycle lengths, and the degree of vertices adjacent to the pendants.
This Discrete Mathematics previous year question is Q26 of the GATE CSE 2012 paper. Find more GATE CSE PYQs on Discrete Mathematics in Engineering Mathematics, or browse all GATE CSE PYQs.
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Discrete Mathematics has 50 GATE CSE PYQs across 23 papers from 2011 to 2026. 11 of them are 2-mark MCQs like this one, and GATE CSE 2012 has 2.
How GATE tests Discrete MathematicsIndependent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.