题目:
If n > 2, then the sum, S, of the integers from 1 through n can be calculated by the following formula: S = n(n + 1)/2. Which one of the following statements about S must be true?
选项:
A、AS is always odd.
B、BS is always even.
C、CS must be a prime number.
D、DS must not be a prime number.
E、ES must be a perfect square.
答案:
D