From Too Good to Be True: The Colossal Book of Urban Legends, by Jan Harold Brunvand
A final exam had just one question: "Write the best possible final exam question for this course, then answer it."
One student immediately wrote, "The best possible final exam question for this course is 'Write the best possible final exam question for this course, then answer it.'"
The student also could have simply written "the best possible final exam question for this course, then answer it."
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