- I was secretly smoking when my father walked into my room.To my surprise,he wasn't angry.

问题描述:

- I was secretly smoking when my father walked into my room.To my surprise,he wasn't angry.
- I was secretly smoking when my father walked into my room.To my surprise,he wasn't
angry.
-- Well,tell us -- what when your father discovered you?
A.did happen B.has happened C.is happening D.was happened
为什么选A,D不行?

D妥妥的不行,因为happen、take place这些表示发生的动词是没有被动的,也就是肯不会跟be动词连用.
A实际上是强调到底发生了什么,就把助动词独立出来happened变为did happen