1.We must obey the library rules.
我们必须听从那儿的图书管理员.
2.We must observe the library rules.
我们必须遵守图书馆的规则.
3.You are here in the library. You must obey library rules. You mustn't smoke. You mustn't little the floor.
你到了图书馆,就必须遵守图书馆的规定,不能吸烟,不能往地板上乱扔东西.
4.You must comply with the library rules.
你必须遵守图书馆的规则.
5.You mustn't talking loudly in the library .
你不许大声说话在图书馆