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:考查时态。had to提示是一般过去时,发生在“过去的过去”的事情,用过去完成时,排除A、B;until引导的时间状语从句的时态要与主句一致,故用过去时,排除D。故选C。