为什么用who is it 而不用who are you?

为什么用who is it 而不用who are you? It is I who am to blame.为什么who 后面用am 不用 is? it is always the people who live together.为什么这里用it is而不用they are 这有一个英语语法题,关于强调句型.it is professor Li who teach us English为什么不用that而用who 新概念第六课课后习题This flowerpot is broken. Who knocked it over?这里为什么用knocked it over,而不用knocked it off? 是谁呀who is it?为什么用it不用she或he? （ what ）is she -------she is my aunt 为什么用what 而不用 who It is I who want to see you.中为什么用I 不用me Who do you _the most famous basketball player?为什么用think is 而不用think? He is the man which he was.这里为什么不用who而用which呢, so i didn't ask who it was,为什么不用Who that was !为什么要用who it was It makes no difference (who) we will share the office with为什么用who不用whom Who looks after Rose 为什么这里要用looks而不用Who does look after Rose? The mother didn't know who to blame for the broken glass as it happened while she was out.为什么用who 而不用whom啊? Jack (whom) I teach is lazy 这句中为什么用whom而不用whoJack (whom) I teach is lazy 这句中为什么用whom而不用who呢 Mum,this is kate,who I knew in Paris.为什么用who不用whom? Phone #对不?为什么不用at?what's this in English?怎么回答?有this is的形式么?还有who's this?是不是用it's的回答而不用this is? The flowerpot is broken,who knocked it over?为什么用over不能用off吗?为什么用over不用off？