Unless we spend money to spot and preventasteroids( 小行星 )now , one might crash into Earth anddestroy life as we know it , say some scientists.  Asteroids are biggerversions of the meteoroids( 流星 )that race acros s the night sky.Most orbit the sun far from Earthand don't threaten us.But th ere are also thousads whose orbits put them on acollision course with Earth.  Buy $ 50 million worthof new telescopes right now.Then spend $ 10 million a year for the next 25years to locate most of the space rocks.By the time we spot a fatal one , the scientists say , we'll have a way to change itscourse.  Some scientists favorpushing asteroids off course with nuclear weapons.But the cost wouldn't becheap.  Is it worth it? Twothings experts consider when judging any risk are: 1) How likely the event is;and 2) How bad the consequences if the event occurs.Experts think an asteroidbig enough to destroy lots of life might strike Earth once eve ry 500 , 000 years.Sounds pretty rare-but ifone did fall , it would bethe end of the world.“If we don't take care of these big asteroids , they'll take care of us , ”says one scientist.“It's thatsimple.”  The cure , though , might be worse than the disease.Dowe really want fleets of nuclear weapons sitting around on Earth?“The world hasless to fear from doomsday( 毁灭性的 ) rocks than from a great nuclear fleet set against them , ” said a New York Times article. 1. What does the passage say aboutasteroids and meteoroids? A) They are heavenly bodies different incomposition. B) They are heavenly bodies similar innature. C) There are more asteroids thanmeteoroids. D) Asteroids are more mysterious thanmeteoroids. 2. What do scientists say about thecollision of an asteroid with Earth? A) It is very unlikely but the dangerexists. B) Such a collision might occur once every25 years. C) Collisions of smaller asteroids withEarth occur more often than expected. D) It's still too early to say whether sucha collision might occur. 3. What do people think of the suggestionof using nuclear weapons to alter the course of asteroids? A) It sounds practical but it may not solvethe problem. B) It may create more problems than itmight solve. C) It is a waste of money because acollision of asteroids with Earth is very unlikely. D) Further research should be done beforeit is proved applicable. 4. We can conclude from the passage that________. A) while pushing asteroids off coursenuclear weapons would destroy the world B) asteroids racing across the night skyare likely to hit Earth in the near future C) the worry about asteroids can be left tofuture generations since it is unlikely to happen in our lifetime D) workable solutions still have to befound to prevent a collision of asteroids with Earth 5. Which of the following best describesthe author's tone in this passage? A) Optimistic B) Critical C) Objective D) Arbitrary