I hope which it will be sunny tomorrow 这里可以填WHICH吗.为什么.

I hope that it will be sunny tomorrow
这里不用which,这是一个宾语从句,从句中不缺任何成分,只能用that引导宾语从句.
由连接词that引导宾语从句时,that在句中不担任任何成分,在口语或非正式的文体中常被省去,
例如：
He has told me that he will go to Shanghai tomorrow.他已经告诉我他明天要去上海.
which 基本释义：
pron.哪/那一个；哪/那一些
adj.哪一个；哪一些哪种宾语从句中用which。谢谢宾语从句which是一个连接代词,在宾语从句中可以充当主语，宾语或定语。意思是“哪一个，那些”如：I don't know which bike belongs to my father. I wonder which is better ,this one or that one? He asked me which I liked best. I don't know which book is yours.我不知道那本书是你的 He asked which books were his 他问那些书是他的