When we go to the library, we must be _____ in the library.

This is my friend. ____ name is Bob and ____ is 12 years old.

下列各句中没有错别字的一项是（ ）

Come on! The man in charge of the job ___ you have to explain everything is waiting.

______the Internet is of great help, I don’t think it’s a food idea to spend too much time on it