The time I first spend with Nelson Mandela was a very difficult period of my life.Awhe

问题补充：

The time I first spend with Nelson Mandela was a very difficult period of my life.

Awhen

Bwhich

Cof which

Dat which

答案：

A. when

(答案→)B. which

C. of which

D. at which

解析：句意：我第一次和曼德拉度过的时光是我生命中非常困难的一段时期。这个句子包含一个定语从句，且关系词在从句中作宾语，指物，故用关系代词 which，选B。