My parents___here last night,but they couldn't.

问题描述:

My parents___here last night,but they couldn't.
A.were to have come
B.must have come
C.came
D.had to come
这道题跟没写完全似的.该怎么翻译呢?为什么呢?

此题考察虚拟语气.
本句的意思是
我父母昨晚原本要来的,但他们没能来
My parents would have come here last night,but they couldn't
这里were to have come 等同于would have come 表过去将来