Im interested in ______you have said.
A. all that B. all what C. that D. which
老师你好，我想问这道题为何不选择 that 或者 which。望回复，谢谢老师！
答案是选项A。句意：我告诉你的所有都有兴趣。all“所有；所有些事；全部”是先行词作介词in的宾语，that引导定语从句修饰all；B选项错在what不可以引导定语从句；选项C或选项D可引导定语从句，但前面都没被修饰的先行词，故也应排除。
▲注意区别以下句子：
He told us all that he had seen.他告诉大家他所看到的所有。（all为直接宾语，that引导定语从句修饰先行词all）
He told us all what he had seen.他告诉大家所有些人他看到了什么。（all作间接宾语us的同位语，what引导名词性从句作直接宾语，且在从句中作had seen的宾语）
He told us all that he had seen the stoken car.他告诉大家所有些人他看到了那辆失窃的轿车。（all作间接宾语us的同位语，that引导名词性从句作直接宾语，that在从句中不担当成分）
