—You see，I’m poor in maths，you are not good at English，and...

—That’s________we should help each other.

A．when

B．where

C．how

D．what

弯曲试验设备应有足够硬度支承辊，其长度应（）试样的宽度或直径。

A.等于

B.大于

C.小于