必须；义务＝have to/have got to (过去式为had to)
(否定为need not/don't have to/don't need to)
We must (= have to) obey the law. 我们必须守法。
All the drivers must wear seatbelts. 所有的驾驶员都必须系安全带。
The little boy must (= has to) keep quiet in the theater.
It's getting late. I really must go. 天晚了，我真的得走了。
Must I make a reservation in advance?
No, you needn't/don't have to.
Do I have to make a reservation in advance?
Yes, you do./No, you don't.
我必须事先订位吗？ 不必。内容来自 听力课堂网：http://www.tingclass.net/show-5855-216033-1.html