Question

10.Helen ___ her key 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详细解析为什么选C

Answer 1

c,
she had to wait 这句可以看出时态是过去，until 后也用一般过去时。排除D。把钥匙落在办公室是在等她丈夫之前 ，时态应该是过去的过去，即过去完成时，所以第一空先可以排除A。B。故选C。

Answer 2

这个是时态问题，如果had to是has to的话就得选A。