在图书馆必须保持安静用英文怎么说It's_____ ______ _____ _____in the library
问题描述：
在图书馆必须保持安静用英文怎么说
It's_____ ______ _____ _____in the library
答
has to be quiet
答
necessary to keep slient
答
must to be quiet
答
time to keep silent
答
necessary to keep silent