The fan(that/which) you want is on the desk.The magazine (that/which)he has taken away is mine.The train that/which ws going to nanning was late.(这里不可省,因为做主语)
The train which|that is going to nanning was late. The train which was late was going to nanning. The magzine which/that he has taken away is mine. The fan is on the desk which/that you want it.