题目内容
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops. （26）是（）
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In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz). （18）是（）
Questions 11 to 18 are based on the conversation you have just heard.
Questions 11 to 18 are based on the conversation you have just heard.
Questions 11 to 18 are based on the conversation you have just heard.
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