gwd7-36

guafafd

If a and b are positive integers such that a – b and a/b are both even integers, which of the following must be an odd integer?

A. a/2

B. b/2

C. a+b/2

D. a+2/2

e b+2/2

the key is D.

请问怎么推出来的。

guafafd

那为什么 e不对呢?

如果不知道d是答案，你怎么推算呢？