There was a question for less than $1,000 that could have given us Ada programmers some difficulty because we know too much.  It was

Which of the following is NOT an integer?

(A) 1 (B) 2 (C) 1/2 (D) -1

The contestant answered "C" and was right.  But suppose the contestant had said, "-1 is a simple expression, so it isn't an integer.  (It isn't even a number.) That's my final answer."