If引导的条件状语从句中的虚拟语气
表示对过去情况的虚拟:
从句:had done
主句:would/could/might/should have done
If I had read the book,I would have told you about it.
如果我读了这本书,我就会告诉你了。
表示对现在情况的虚拟:
从句:would/could/might/should do
主句:动词过去式
If he studied at this school,he would know the environment around the school very much.
如果他在这所学校学习的话,他会很了解周边环境。
表示对将来情况的虚拟:
从句:should do/were to do
主句:would/could/might/should do
If he should go to Harvard University,he would make full use of his time.
如果他要上哈佛大学的话,他就会充分利用他的时间了。