为什么He'll do what he can to study hard.这句话中What 不可以改成that

为什么He'll do what he can to study hard.这句话中What 不可以改成that He'll do what he can to study hard.这句话是什么从句,what可不可以改为that I'll do what we can to study English well,为什么这句话中要用to study He tries to do what he can _________English well(study) what he needs is to study hard I want to know what he said 为什么what 不可以换成that 句子what I can do is to study hard.为什么要有to? He thinks that he can concentrate on what he likes to do aft I am going to do that I want to do 这句话that应该改成what为什么`` what is it that he wants to do?这句话对吗? 为什么说He always tires to do what he can to help his classmates He ll tell you what to do 是什么从句?