原本的假設語句是:-->與過去相反的假設If S + had + pp, S + would have + pp. If I had known that you were taking the same route to school as we, I would have suggested you riding in the same car with John and me. 改成倒裝句就變成: Had S + PP......, S would +pp. Had I know you were taking the same route to school as we, I would have ..