试题题干
Translate the following sentence into Chinese.
It's not particularly proper to use radio communication unless on certain wave lengths that are absorbed by the atmosphere.
参考答案
试题解析
考点：radio communication 无线电通信；certain wave length特定波长；be absorbed by 被···吸收。
句子结构：考察It's not···unless···句型，意为除非·····否则······。that are absorbed by the atmosphere为定语从句修饰certain wave lengths。