填空题

Unless we spend money to spot and prevent asteroids, i.e. minor planets, one might (36)________ into earth and destroy life as we know it, say some scientists. Asteroids are bigger (37)________of the meteoroids that race across the night sky. Most orbit the sun far from earth and don’’t (38)________us. But there are also (39)________whose orbits put them on a (40)________course with earth. Buy $50 million worth of new (41)________right now. Then spend $ 10 million a year for the next 25 years to locate most of the space rocks. By the time we (42)________a fatal one, the scientists say, we’’ll have a way to change its course. Some scientists favor pushing asteroids off course with nuclear (43)________. But the cost wouldn’’t be cheap. Is it worth it Two things experts consider when judging any risk are: (44)________________Experts think an asteroid big enough to destroy lots of life might strike earth once every 500,000 years. (45)________________. "If we don’’t take care of these big asteroids, they’’ll take care of us," says one scientist. "It’’s that simple." The cure, though, might be worse than the disease. (46)________________ "The world has less to fear from doomsday rocks than from a great nuclear fleet set against them," said a New York Times article.