How often does the magazine _____—Once a month.

He always appears to .—That’s because he’s really knowledgeable and experienced.

What ______ the number of the students in your school–About two thousand. A number of them _____ from the countryside.

.It was in the 1990s _______ we were working together ____ we made friends with each other.

下列各句中，没有语病的一句是