问题补充:
Our neighbor offered to look after our baby yesterday when we were busy, is often the case.
A. it
B. that
C. which
D. as
答案:
A. it
B. that
C. which
(答案→)D. as
解析:考查定语从句。这里考查由as引导的非限定性定语从句,as在句中由“正如”之意。句意:昨天当我们都很忙的时候,我们邻居主动来照顾我们的婴儿,通常就是这样的。故D正确。