【问】 按照语法规则，在含有since从句的主句中要使用完成体形式。如果主句中有情态助动词时该怎么办呢?

【答】 含有since从句的主句中含有情态助动词时，可以使用非完成体形式：

1. (Ever) since my teeth were pulled out I can’t eat anything solid.

自从我拔了牙以后就不能吃固体食物。

2. I have to use crutches (ever) since I had a car accident.

自从我出了车祸后，我就得用拐杖了。

3. They won’t smoke (ever) since they saw a film on lung cancer.

他们看了一部有关肺癌的影片后，就坚决不再吸烟了。

4. He can’t get about much since he had that accident.

他在那次事故后就不能多走动了。