當(dāng)主句與if條件句中的動(dòng)作都發(fā)生在過(guò)去時(shí),主句謂語(yǔ)動(dòng)詞就要使用had done形式,if條件句中謂語(yǔ)動(dòng)詞則要使用would have done形式 .e.g.If I had worked hard,I would have passed all the exams.
當(dāng)主句以及if條件句中的動(dòng)作都發(fā)生在現(xiàn)在時(shí),主句的謂語(yǔ)動(dòng)詞必須使用did(be動(dòng)詞用were),if條件句動(dòng)詞須使用would do形式.e.g.
If he came on time for the meeting,I would treat you to a rich meal.
If I were you,I would go with him.
當(dāng)主句和if條件句的動(dòng)作都發(fā)生在將來(lái)時(shí),主句動(dòng)詞可以使用did,should do 或were to do形式,if條件句中動(dòng)詞須使用would do形式.
e.g.If you kept/should / keep were to keep your promise,you would earn more than trust.