If n is an odd integer less than 10, which of the following must also be an odd integer?  Choices:
A) 2n + n^2 + 2  B) n^3 + 2n  C) 3n + 2^n  D) n^3 + 1  E) 3n
Answer: n^3 + 1   A: 2n = even   B: 3n = even   C: 3n + n^2 + 2 = even   n^3 + 1: n^2 + 1 = odd   E: 2n + n^2 = even   Answer: n^3 + 1
<result>D</result>
If n is an odd integer less than 10, which of the following must also be an odd integer?