【单选题】

Passage 1Robert is nine years old and Joanna is seven. They live at MountEbenezer. Their father has a big property. InAustralia they call a farm a property.Robert and Joanna like school very much.At school they can talk to their friends but Robert and Joanna cannot see their friends. They live 100, perhaps 300 miles away and like Robert and Joanna, they all go to school by radio.MountEbenezer is in the center ofAustrali

A、Not many people live in “theCenter”. There are no schools with desks and blackboards and no teachers in “theCenter”. School is a room at home with a twoway radio. The teacher also has a twoway radio.Every morning she calls students on the radio. When all students answer, lessons begin... Think of your teacher 300 miles away！ When children are having a lesson, they can hear their teacher.
A、but their teacher cannot hear them
B．and their teacher can hear them, too
C．but cannot hear their schoolmates
D．and see him or her at the same time