问题补充:
Helen her keys in the office so she had to wait until her husband home.
A. has left; comes
B. left; had come
C. had left; came
D. had left; would come
答案:
A. has left; comes
B. left; had come
(答案→)C. had left; came
D. had left; would come
解析:考察时态。根据句意可知,Helen因为先把钥匙丢在了办公室,所以她要等她的丈夫回家。
所以leave发生在had to wait之前,即过去的过去,用过去完成时,第二空是until引导的时间状语从句,从句中用一般过去时表示过去将来。