You mustn't speak loudly in the library.
你不能在图书馆大声说话。
You mustn't eat or smoke in the library.
你不能在图书馆吃东西或抽烟。
You mustn't damage the book or graffiti on the book.
你不能损坏书籍或在书上乱涂乱画。
You mustn't take the book away without consent.
未经允许你不能带走图书馆的书籍。
这些是最基本的...