Suppose Prof. N is giving Mr. M an exam, and Mr. M doubts that a question on the exam paper is wrong. Mr. M asks Prof. N about it. Naturally Prof. N will be careful to give a response so that he doesn't reveal any clue about the answer to that question.

So can Prof. N convince Mr. M that the exam paper is correct without giving any clue about the answer?

Looks like if the question was Find the Isomorphism between 2 graphs G1 and G2 then Prof. N has a way.

Note: In all that is stated above any resemblance to any real character is pure coincidence.