1. 表示现在/过去/将来情况的虚拟条件句

　　虚拟条件句主要有三种结构：
　　1)　表示与现在情况相反：主句谓语用“would / could / might +动词原形”，从句谓语用“动词的一般过去时”(动词be的过去式一律用were)。
　　If I were you, I would not accept his offer.
　　If I had time, I would certainly go to the cinema with you.

　　2) 表示与过去情况相反：主句谓语用“would / could / might + have +过去分词”，从句谓语用过去完成时。
　　If I had got up a little earlier, I wouldn’t have missed the train.
　　If I had been more careful, I might have passed that exam.

　　3) 表示与将来情况相反：主句谓语用“would / could / might +动词原形”，从句谓语用“were +动词不定式”或“should +动词原形”。
　　If I were to do the job, I would not be able to have enough time to study.
　　If it should rain tomorrow, I would not go out with you.