最常用2种虚拟语气：

1. should have done 本该做某事而没有做，如：I shouldn't have told him the truth.我本不该告诉他真相的（事实上告诉了）。

2. if ... would ... 如果......，将会......，不可能发生的假设，如：If I were u, I would choose him.如果我是你（不可能），我会选择他。