Everyone has periods in their liveseverything seems very hard.A. whenB. whereC. whichD.

问题补充：

Everyone has periods in their liveseverything seems very hard.

A. when

B. where

C. which

D. that

答案：

(答案→)A. when

B. where

C. which

D. that

解析：考查定语从句。when引导的是定语从句，修饰先行词periods。