If n is an even integer, then which of the following must be an odd integer?  Choose the correct choice from the following answers:
A) 2n B) 3n C) 3n + n^2 + 2 D) n^2 + 1 E) 2n + n^2
Answer: n^2 + 1   A: 2n = even   B: 3n = even   C: 3n + n^2 + 2 = even   n^2 + 1: n^2 + 1 = odd   E: 2n + n^2 = even   Answer: n^2 + 1
<result>D</result>
If n is an even integer, then which of the following must be an odd integer?