Class begins()nine o'clock.It is over()quarter()twelve.Lunch begins()twelve.They are talking()some Americans()a map()ChinaI am not listening()music.I am working() the computer填适当的介词

Class begins()nine o'clock.It is over()quarter()twelve.Lunch begins()twelve.
They are talking()some Americans()a map()China
I am not listening()music.I am working() the computer
填适当的介词

Class begins (at) nine o'clock.It is over (at) quarter (to) twelve.Lunch begins (at) twelve.
They are talking (with) some Americans (about) a map (of) China.
I am not listening (to) music.I am working (on) the computer.

Class begins(at)nine o'clock.It is over(at)quarter(to)twelve.Lunch begins(at)twelve.
They are talking(about)some Americans(for)a map(of)China
I am not listening(to）music.I am working(on) the computer
自己想的 错的还请指教~~~

about with in
to at