听力原文： Hotlines have become common in China. Some radio broadcasting stations use hotli

nes to encourage the listeners to take part in the talk shows. [18] That's a good idea. Yet, the fact is, some people do nothing but break the whole programme. 5ome people know little about the topic under discussion. Sometimes they do not even know what the host is talking about. So the host has to tell the caller what the show is about. Usually the caller will ask a few questions which express his hope and show his ignorance. Then the host has to answer and explain—how silly this is! It wastes a lot of time. It seems that some people phone the hotlines for fun. They just want to let the listeners hear them. [19] They don't care what the topic is, whether they themselves are interested in or how silly they appear to be. I'm totally bored by those people. [18]/ [20] It's necessary for radio stations to improve the hotline programmes. In my opinion, If a caller doesn't know what is going on, the operator should not let the caller take part in it.

It can be inferred from the passage that

A．some radio broadcasting stations use hotlines for advertisements.

B．it is not a good idea for some radio broadcasting stations to use hotlines.

C．some people use hotlines in a wrong way.

D．some people have unclear thoughts.