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  3. Unless we spend money to spot and prevent asteroids now, one might crash into Earth and destroy life as we know it, say some sci

Unless we spend money to spot and prevent asteroids now, one might crash into Earth and destroy life as we know it, say some sci

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问题     Unless we spend money to spot and prevent asteroids now, one might crash into Earth and destroy life as we know it, say some scientists.
    Asteroids are bigger versions of the meteorites that race(1)______ the night sky. Most(2)______ the sun far from Earth and don’t threaten us. But there are also thousands(3)______ orbits put them on a collision course with the(4)______.
    Buy $50 million worth of new telescopes right now. Then spend $10 million a year for the next 25 years to (5)______ most of the space rocks. (6)______ we spot a fatal one, we’ll have a way to change its(7)______, the scientists say.
    Some scientists(8)______ pushing asteroids off course with nuclear weapons. But the cost wouldn’t be cheap. Is it(9)______ it? Two things experts consider when judging any (10)______ are how likely the event is and how bad the(11)______ if the event occurs. Experts think an asteroid (12)______ enough to destroy lots of life might strike Earth once every 500,000 years. Sounds pretty(13)______ — but if one did fall, it would be the (14)______ of the world. "(15)______ we don’t take care of these big asteroids, they’ll take care of us. It’s that(16)______," says one scientist.
    The(17)______, though, might be worse than the disease. Do we really want(18)______ nuclear weapons sitting around on Earth? "The world has(19)______ to fear from doomsday rocks than from a great nuclear fleet (20)______ them," said a New York Times article.
(15)
选项 A、Unless
B、If
C、Because
D、Since
答案B
解析 关联词题。此题可以用排除法，该句前后两部分并不构成因果关系，故排除C、D。unless不符合逻辑。B为正确答案。
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