I often think of the days _____ I stayed with the experts, _____ has a great effect on my job.

A． when , which

B． when, who

C． that, which

D． which, that

曲轴表面缺陷主要是（）和（）。

A．粗糙度／油孔

B．截面变化／粗大刀痕

C．截面变化／油孔

D．粗大刀痕／粗糙度