Question

Bob called to tell his mother that he couldn’t enter the house, for he ________ his key at school

1. A.
   had left
2. B.
   would leave
3. C.
   was leaving
4. D.
   has left

Answer 1

A
该句句意为Bob打电话给他的妈妈，告诉她说他进不了房门，因为他把他的钥匙忘在学校了。根据句意可知，把钥匙忘在学校（leave）的动作发生在打电话（called）之前，called 是过去时，那么忘记钥匙在学校leave就是发生在过去的过去，即过去完成时，故选择A项。
【考点定位】考察时态。