标题: 狒狒一道逻辑题求解！！！！！ [打印本页] 作者: ricky27 时间: 2013-10-19 06:23 标题: 狒狒一道逻辑题求解！！！！！ 39. Quasars---celestial objects so far away that their light takes at least 500 million years to reach Earth---have been seen since 1963. For anything that far away to appear from Earth the way quasars do, it would have to burn steadily at a rate that produces more light than 90 billion suns would produce. But nothing that burns at a rate that produces that much light could exist for more than about 100 million years.
If the statements above are true, which one of the following must also be true on the basis of them?
A. Instruments in use before 1963 were not sensitive enough to permit quasars to be seen.
B. Light from quasars first began reaching Earth in 1963.
C. Anything that from Earth appears as bright as a quasar does must produce more light than would be produced by 90 billion suns.
D. Nothing that is as far from Earth as quasars are can continue to exist for more than about 100 million years.
E. No quasar that has ever been seen from Earth exists any longer.
这个题为什么选E？No quasar that has ever been seen from Earth exists any longer. 这里我想的是，既然不知道什么时候从地球上能观测到Quasars，那也就不知道它在地球上被观测了多久。假如是100年前才开始观测到的呢，即使光线travle了500万年才到这里，那么观测到这个星辰燃尽也应该是几百万年之后的事了，难道是我物理没学好？