4.Occasions are quite rare I have the time to spend a day with the kids.
A. who
B. which
C. why
D. when
网友回答
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。