四、閱讀測驗【請依照段落上下文意，選出最適當的答案】
       Space X—the American technology company—launched 60 satellites into space in January 2020. Space Xplans to create a network of 12,000 satellites. The company says that the network, known as Starlink, will helpprovide better Internet service to remote parts of the world. But astronomers say the growing number of satellitesorbiting the Earth is making it harder for them to observe and learn from the universe.        Satellites are made of metal that reflects sunlight. This makes them show up in the night sky as bright,slow-moving dots. After the launch, the Starlink satellites appeared in images taken by telescopes and deep-spacecameras as a line of bright lights flying across the sky. Astronomers learn about space by using large telescopesand special cameras to observe light coming from very far away. The information they collect can help themunderstand things like how galaxies are formed or which planets might be able to support life.        Some astronomers also use radio telescopes, which record radio waves coming from space. This makes itpossible to study things that give off low energy and would not show up as light—like dust and gases. In April2019, astronomers used information collected by several radio telescopes to produce the first image of a blackhole. Large groups of satellites—known as “satellite constellations”—give off radio signals of their own andreflect radio waves coming from Earth. These extra signals interfere with radio waves coming from further awayin the galaxy. While it might be possible to build satellites with surfaces that don’t reflect light, it will be verydifficult to make satellites that don’t interfere with radio waves.
【題組】21. What is the passage mainly about?
(A) Space X the technology company
(B) Satellites and their contribution to communication
(C) The problems with too many satellites in space
(D) What satellite constellations really are