that 在定语从句里是关系代词,不可以在从句里作状语：why是关系副词可以做从句原因状语 例：the reason why i do this is just for you .the reason that i told you yesterday .楼主试比较.也就是说,关系副词作状语,代词做主,宾语.看不懂,不动就追问.