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The number of vertices of odd degree in any graph of 'n' vertices with 'e' edges is :

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Correct answer: B. even

Explanation

By the handshaking lemma, the sum of the degrees of all vertices in a graph equals 2e, which is always an even number. If the count of odd-degree vertices were itself odd, the sum of their degrees would be odd, and adding the even sum contributed by the even-degree vertices would make the overall total odd, contradicting the handshaking lemma. Therefore the number of vertices of odd degree in any graph must always be even.

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