阅读理解.Many objects in the universe are invisible,but they send radio waves. The radio telescope thus

文章大意：本文主要介绍了无线电天文望远镜，详细介绍了它的发明、构成、工作原理、作用等。
【12题详解】
细节理解题。根据文中的信息A radio telescope is usually made up of：One or more antennas to collect the radio waves.可知，无线天文望远镜帮助收集宇宙中的无线电波，故答案选C。
【13题详解】
细节理解题。根据文中的信息Most antennas are made in the shape of a dish to collect and reflect, the radio waves to the sub-reflector, in the same way as a curved mirror focuses visible light to one point.可知，大多数无线天文望远镜的天线都是碟形的，用来将无线电波聚焦在副反射器上，故答案选D。
【14题详解】
词义猜测题。根据下文and keep the telescopes sensitive, radio telescopes are built in places where there are no human radio waves or electronic signals.可知是为了避免干扰，保持望远镜的灵敏度，无线天文电望远镜建在没有人类无线电波或电子信号的地方。所以"interferences"指的是来自人类的无线电波和电子信号，故答案选D。
【15题详解】
细节理解题。根据文中的信息This is extremely useful, because there are objects that can't be seen, objects that we wouldn't even know without radio telescopes.可推知，在无线天文望远镜的帮助下，我们发现了宇宙中一些未知的物体，故答案选C。