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.

题库:计算机网络管理员 类型:最佳选择题 时间:2017-07-03 13:36:51 免费下载:《单选集》Word试卷

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.optical
B.radio
C.electrical
D.magnetic

本题关键词:噬菌体Ⅱ群71型,肠道病毒71型感染,肠道病毒71型手足口病,肠道病毒71型(EV71)核酸检测试剂盒(荧光PCR法),肠道病毒71型核酸检测试剂盒(PCR-荧光探针法),肠道病毒71型、柯萨奇病毒A16型核酸RNA检测试剂盒（荧光PCR法）;