1个回答
" 带to 的情态动词有四个：ought to， have to， used to， be to， 如加上have got to ，(=must)， be able to，为六个。
它们的疑问，否定形式应予以注意：
Do they have to pay their bill before the end of the month？
She didn‘t use to play tennis before she was fourteen.
You ought not to have told her all about it.
Ought he to see a heart specialist at once.？
ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do 等助动词协助。更多知识点可关注下新东方，课程以培养语言综合运用能力为目标，通过紧贴生活的话题场景来呈现授课内容和语言知识点，让孩子在轻松的课堂中快乐学习，自然习得语言知识和技能，综合提升听说读写能力。"