概念

条件状语从句使用虚拟语气时，要注意假设的时间，即现在、过去、将来。虚拟语气在条件状语从句中有三种变化，主句也有三种变化。

主句谓语变化规则：

1. 过去时：should/would/might/could do
2. 现在时：should/would/might/could have done
3. 将来时：should/would/might/could do

从句谓语变化规则：

1. 过去时：if had done
2. 现在时：if did
3. 将来时：if were to do / should do / did

对过去假设

If I had got there earlier, I should have met here.

If he had taken my advice, he would not have made such a mistake.

对现在假设

If I were you, I would take an umbrella.

If I knew his telephone number, I would tell you.

对将来假设

If he should come here tomorrow, I would talk to him.

If there were a heavy snow next Sunday, we would go skating.

标签：do,would,虚拟语气,从句,should,状语
来源： https://www.cnblogs.com/shiramashiro/p/16147311.html