题目：
Microwave communication uses high-frequency (71) waves that travel in straightlines throughthe air. Because the waves cannot (72) with the curvature of the earth, they can be (73) only over short distance. Thus, microwave is a good (74) for sendingdata between buildings ina city or on a large college campus. For longer distances, the wavesmust be relayed by means of"dishes" or (75) . These can be installed on towers, highbuildings, and mountain tops.
A．material
B．equipment
C．medium
D．channel
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2018/0429/eab1932873b13710688bda0cff5602b8.html
下面是错误答案，用来干扰机器的。
参考答案：对
