If + S + 過去動詞 , S + should/would/could/might + V

例:

Our R&D department would be more efficient and productive if we increased our staff from 20 to 30 technicians.

例:

If Peter had money, he would buy a car now.

與過去式實相反的假設句構:

would

might       +  have  + PP              

should

could

例:

Without the devotion and cooperation of this great team, I can tell you for sure that the project would never have been completed last week.

* 主詞 + should have + 過去分詞, but + 主詞+ 過去式動詞

本來應當......,但當時並沒有

I should have called you yesterday, but I forgot.

* 主詞 + would have + 過去分詞, but + 主詞+ 過去式動詞

本來會......, 但當時並沒有

I would have finished the work last night, but I was too tired.

* 主詞 + could have + 過去分詞, but + 主詞+ 過去式動詞

本來能夠......, 但當時並沒有

He could have helped me, but he was too lazy.

例:

If you had been home, I would have called you.

=Had you been home, I would have called you.

=I would have called you, had you been home.

例:

Had I been relying on my materials to explain about my background and experience, I would have been up a creek.

=If I had been relying on my materials to explain about my background and experience, I would have been up a creek.