问题
选择题
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
答案：C
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。
