4.Occasions are quite rare I have the time to spend a day with the kids. A. who B. whichC

问题补充：

4.Occasions are quite rare I have the time to spend a day with the kids.

A. who

B. which

C. why

D. when

答案：

A. who

B. which

C. why

(答案→)D. when

解析：此题中occasions为先行词，occasion本意为a time when something happens，所以属于时间的范畴。而且后面的句子中缺少时间状语，所以应该用when连接。如果要用which，需要改写为 on which才可以。