On the knowledge test, how many answers are complete and correct?

• A. All of the above are correct.
• B. Two answers are complete and correct.
• C. Only one answer is complete and correct.
• D. No answer is completely correct.

Answer: (C)

This item tests how to handle a self-referential statement and keep the logic internally consistent. If exactly one answer is complete and correct, that one must be the statement that claims this fact. That makes the claim self-validating: there is indeed only one correct answer, and it is the statement that says so. All other statements would then be false—“All of the above are correct” would imply more than one correct, “Two answers are complete and correct” would imply a different count, and “No answer is completely correct” would be contradicted by the existence of this single correct answer.

If you assume any other statement is the sole correct one, you quickly get a contradiction: either more than one would be correct (if the all-encompassing option were true), or none would be correct (which would itself negate that option). The only consistent resolution is that there is exactly one correct statement, and it is the one that asserts that fact.