如果条件句中的动作和主句的动作不是同时发生，主句和从句的谓语动词的形式应分别根据各自所表示的时间加以调整。
1)If I had received the passport yesterday, I would start today.
2)If he had telephoned me last night, I would see him now.
3)If he had followed the doctor’s advice, he would be all right now.
4)If China had not been liberated, the working people would still be leading a miserable life.
