How are the kids spending their childhood? I can’t help recalling（回忆）that there was a time

问题补充：

How are the kids spending their childhood? I can’t help recalling（回忆）that there was a time we played happily and freely in the outside.

A. that

B. which

C. when

D. 不填

答案：

A. that

B. which

(答案→)C. when

D. 不填

解析：考查定语从句。本定语从句的先行词是a time，定语从句的结构很完整，故使用关系副词when.句意：我情不自禁地回想起那一段我们在外面开心自由玩耍的日子。故C正确。