A、It forces one to form pictures in the mind. B、It provides many interesting programs. C、It teaches people how to imagine things

The most obvious difference between radio and television is that you listen and look at the television, but just listen to the radio. In this way, radio is more imaginative because it forces you to form pictures in your own mind rather than providing you with visual information, which is what television does.
    In addition, radio is more flexible than television, since you don’t have to be in the same room as the radio set in order to listen to the programs, but you do have to be in the same room as a television in order to watch it.
    A radio is also far more portable than a television. You can listen to the radio while driving in the car, jogging or even just walking around. Although portable televisions do exist, you can’t really watch one while you are jogging, for example.
    One of the main advantages of radio, however, is that it offers the listener more immediate access to information. Most radio stations broadcast news reports at regular half-hour or hourly intervals, but television news is only broadcast a few times each day. Also, the variety of topics you get on the radio is much greater than that on television.
    Radio is more personal than television. Many radio programs are interactive in a way that television can never be. Listeners can call the radio station they are listening to and express their thoughts and opinions live on air. You can’t ring up a television station and express your opinions, can you?
19. In what way does the speaker say radio is more imaginative?
20. According to the speaker, what is one of the main advantages of radio?
21. Why does the speaker say radio programs are more interactive than television?
22. What does the passage mainly talk about?