问题
选择题
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
答案：D
题目分析：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。