We have to be quiet in the library划线提问（ be quiet ）
问题描述：
We have to be quiet in the library划线提问（ be quiet ）
答
What do we have to do in the library? 是对be quiet都划线的提问。
How do we have to be in the librart?是对仅仅quiet划线的提问。
答
What do we have to do in the library?不要误认为be quiet是由系动词的成分，句子中已经有动词have to了，所以有do提问，把be quiet划去，这是一个动作成分了，所以要用do来代替，前一个do是助动词，后一个是动词
答
What do we have to do in the library?
答
What do we have to do in the library?
这句的改法是将划线部分去掉前面加上不定疑问代词What，又因为有实意动词have to所以要加上助动词do