If x, y, and z are positive integers, is x-y odd?
(1) x=z^2
(2) y=(z-1)^2

 x-y=(2z-1)*1-->奇数

所以C

谢谢!!!

Smart answer.

I can elaborate it.

x-y=z^2 -z^2+2z-1

=>x-y =2z-1

We know any number multiplied by 2 is even. And if 1 is deducted from it

that becomes odd.

So, x-y is odd.

Am I right??