问题
选择题
It was a serious mistake, ______ caused by carelessness.
A．which I think was
B．which I think it was
C．I think which was
D．that I think it was
答案
答案：A
考查定语从句。句中I think为插入语，先行词为a serious mistake，在从句中作主语。句意：它是一个严重的错误，我认为是有粗心引起的。