1. It's cheaper to build radio towers than to string lines across mountain ridges,
    建造无线电发射塔要比翻山越岭架设线路更便宜。

2. Fortunately, a pilot saw the signal and sent a message by radio to the nearest town.
    幸运得很，一位飞行员看到这个信号，用无线电给最近的城镇发了报。

3. Finally, they divided the room in two and gave up on oral communication, communicating primarily through short notes.
    最后她们将房间一分为二，彼此不再讲话，主要通过写便条进行交流。