Mary had to wait outside her house for her husband's return because she （）her key in the office.
A、
has left
B、
leaves
C、
had left
D、
left
【正确答案】：C
【题目解析】：
句意：玛丽不得不在外面等她丈夫回来，因为她把钥匙落在办公室了。根据句意可知，没带钥匙发生在等丈夫回来之前，即过去的过去，用过去完成时。
Mary had to wait outside her house for her husband's return because she （）her key in the office.
Mary had to wait outside her house for her husband's return because she （）her key in the office.
has left
leaves
had left
left
句意：玛丽不得不在外面等她丈夫回来，因为她把钥匙落在办公室了。根据句意可知，没带钥匙发生在等丈夫回来之前，即过去的过去，用过去完成时。