This is the car.The mechanic repaired it yesterday如何用Who,which.whom改为一句话?

题目

This is the car.The mechanic repaired it yesterday如何用Who,which.whom改为一句话?

答案

This is the car which the mechanic repaired yesterday.
It was the mechanic who repaired this car yesterday.
whom只有在人物做宾语的时候才可以用,这里机械师是主语,应该不可以用whom连接.