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

问题描述:

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

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.