英语语法-关于定语从句中的关系代词的问题

Do you know the boy who is standing at the gate? (who)
I don't know whom I am competing with. (whom)
Yesterday I met a girl whose brother is in my class. (whose)
Is this the book which/ that the teacher gave you? (which/ that)
All that needs to be done is done. (all 是不定代词,后面的关系代词必须是that)
The time when China was called the Sick of East Asia is gone.(when)
I know a place where we can find some mushrooms (蘑菇). (where)
The reason why he didn't come to the class is that he was ill. (why)
希望采纳!