the girl (that)you saw in the streets is mary.为什么不用which

the girl (that)you saw in the streets is mary.为什么不用which
the girl (that)you saw in the streets is mary.为什么不用which

the girl (that)you saw in the streets is mary.为什么不用which
which 表示物.那个GIRL是个人啊.
不管怎么样都要用WHO
SO 可以用WHO 也可以用 THAT 就是不用 WHICH

因为which使用在物（非人）
而这个是人可用（who\whom\that）

which修饰物，如果不想用that，只能换成who