题目内容：
根据下列材料，请回答题：Most radio and television stations in the United States are commercial stations,_____26____is tosay, they earn their money from____27____or commercials. Private companies purchase, radio and television ____ 28____from the commercial stations in order to ____ 29 ____ their products. Cable television sta-tions are also ____ 30 ____ stations, though they do not usually have advertisements.____ 31 ____ watch cablestations, people must pay the cable TV company a certain amount of money each ____ 32____.
Public radio and television stations, on the ____ 33 ____ hand, do not have advertisements and peo-ple do not have to ____ 34 ____ to watch them. These stations gain their money ____ 35 ____the govern-ment, private companies, and from some of the ____ 36 ____ who watch or listen to their programs.The ____ 37 ____ government and some large corporations give ____ 38 ____ , large gifts on money, to thepublic stations. Small businesses and people also ____ 39 ____ money to their local public radio and television stations.
ABC, CBS, and NBC are the three ____ 40 ____ commercial radio and television ____ 41 ____ in the UnitedStates. Most local commercial radio and TV stations ____ 42 ____ their programs from one of these na-tional networks. ____ 43____example, each network has a TV news program in the evening, ____ 44____thelocal stations broadcast in addition to their ____ 45 ____ local news programs.
A．that
B．this
C．it
D．which
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答案解析：