The two-way radio is very important to people who live on these great Australian farms. It works much like a telephone. A person can listen to someone else talk and give an answer.
When these radios first came into using, the Australian government set up for them in some areas. At a certain time each day, the boys and girls turn on their radios and listen to teachers in cities miles away. Families on the large farms wanted to give news to their neighbors. "Round Robin (知更鸟) Talks" by radio were started to keep families in touch with each other. They could talk about who was going away or who was sick or who was getting married. The men could talk about their sheep and cattle and how much money the markets would pay for them. In many ways the radio became a newspaper for the farm people of Australia.
This passage tells us something about ______.

A. how large Australia is
B. why the radio is important in Australia
C. how the radio is used in Australia
D. both B and C