题目内容：
Television broadcasts are71to an area that is within the72of the sending station or its relay (中转站)di).73television relays are often placed on hills and mountains so that they can74a wider region, they still cannot cover more land than one from the hilltop75a clear day.However, the rays also go out into the atmosphere, 76there is a relay station on a satel- lite that77around the earth, it can send the pictures to any point on the earth from which the satellite is78Three satellites79turning around over the equator (赤道) send any tele- vision program to any part of the earth. 80makes it possible for world81of newspaper to give the news in all countries at the same time. 82it may be possible for a subscriber (订户) to a televised newspaper to 83a button and see a newspaper page 84his television screen. He could also decide when he wants the page85,86, by dialing different num-ber such as87on a telephone dial, he could choose the language or the edition of the paper he wants to read.
It seems strange to think that, even today, methods of the 88are not entirely useless.
For example, sometimes89agencies which use radio and Telstar also use pigeons to90messages between offices in large cities because the pigeons are not bothered by traffic problems. A．prohibited
B．bounded
C．limited
D．shifted
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