以下提供若干个案例，每个案例下设若干个考题。请根据各考题题干所提供的信息。在每题下面的A、B、C、D、E五个备选答案中选择一个最佳答案。

应首先考虑的原因是

A．鼻咽癌

B．鼻咽纤维血管瘤

C．鼻息肉

D．扁桃体炎症

E．鼻中隔歪曲并鼻甲肥大

Microwave communication uses high-frequency (56) waves that travel in straightlines through the air. Because the waves cannot (57) with the curvature of the earth, they can be (58) only over short distance. Thus, microwave is a good (59) for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (60) .These can be installed on towers, high buildings, and mountain tops.

A．material

B．equipment

C．medium

D．channel