Most radio and television stations in the United States are commercial stations,【C1】______

is to say, they earn their money from【C2】______or commercials. Private companies purchase radio and television【C3】______from the commercial stations in order to【C4】______their products. Cable television stations are also【C5】______stations, though they do not usually have advertisements.【C6】______watch cable stations, people must pay the cable TV company a certain amount of money each【C7】______.

Public radio and television stations, on the【C8】______hand, do not have advertisements and people do not have to【C9】______to watch them. These stations gain their money from the【C10】______, from private companies, and from some of the【C11】______who watch or listen to their programs. The【C12】______government and some large corporations give【C13】______, large gifts on money, to the public stations. Small businesses and people also【C14】______money to their local public radio and television stations.

ABC, CBS, and NBC are the three【C15】______commercial radio and television【C16】______in the United States. Most local commercial radio and TV stations【C17】______their programs from one of these national networks.【C18】______example, each network had a TV news program in the evening,【C19】______the local stations broadcast in addition to their【C20】______local news programs.

【C1】

A．that

B．this

C．it

D．which