分类：教育/科学-外语学习-英语考试
问题：简单的英语问题theteacherdidallthathecou 
the teacher did all that he could to help his student。。。为什么用to help，不用help？he really did not know what to do，weishenmebunengyongwhat he shall do？do you know what to do wh this，为什么不能用how to do ？have trouble understand the text，为什么不是understanding？、i heard she was singingthe teacher did all that he could to help his student。。。为什么用to help，不用help？he really did not know what to do，weishenmebunengyongwhat he shall do？do you know what to do wh this，为什么不能用how to do ？have trouble understand the text，为什么不是understanding？、i heard she was singing a few minutes ago ，为什么用singing？
回答：因为to help 在句中是做目的状语，即老师做那么多的目的是为了帮助他的学生，你记住一个规律是前面已经有一个动词，后面的一个动词通常用不定式表目的或者修饰制约。
当然不用shall,但可以用what he could do .一方面shall 的时态和did 时态不符，另一方面，shall 表达的是强制性的应当怎样，与句子的语气不合。
你颠倒一下 to do with what, what 可以做宾语，而how 不能做作宾语 你自然不能说 to do with how 吧。
应当是understanding。have trouble doing sth .
句子中都有was 了，当然用singing 表过去进行时。