Unless we spend money to spot and prevent asteroids(小行星）now,now might crash into Eanh
and destroy life as we know it,say some scientists.
Asteroids are bigger versions of the meteoroids(流星）that race across the night sky.Most orbit
the sun far from Earth and don.t threaten us.But there are also thousands of asteroids whose orbits put
them on a collision course with Earth.
Buy$50 million worth of new telescopes right now.Then spend$10 million a year for the next 25
years to locate most of the space rocks.By the time we spot a fatal one,the scientists say,we.1l hawe
a way to change its course.
Some scientists favor pushing asteroids off course with nuclear weapons.But the cost wouldn.t be
cheap.
Is it worth it?Two things experts consider when judging any risk are:(1)How likely the evem
is;and(2)How bad the consequences if the event occurs.Experts think an asteroid big enough to
destroy lots of life might strike Earth once every 500,000 years.Sounds pretty rare-but if one did fal,
it would be the end of the world."If we don.t take care of these big asteroids,they.11 take care of us,
says one scientist."It.s that simple."
The cure,though,might be worse than the disease.Do we really want fleets of nuclear weapons
siting around on Earth?"The world has less to fear from doomsday(毁灭性的）rocks than fromt
great nuclear fleet set against them,"said a New York Times article.
What does the passage aay about asteroids and meleoroide?(对应表比较的信号词：第二段
一行的 bigger)
A.They are heavenly bodies different in composition.
B.They are heavenly bodies similar in nature.
C.There are more asteroids than meteoroids.
D.Asteroids are more mysterious than meteoroids.
What do scientists say about the collision of an asteroid with Earh?(对应表示转折的信号同：
第二段第二行中的but)
A. It is very unlikely but the danger exists.
B.Such a collision might occur once every 25 years.
C.Collisions of smaller asteroids with Earth occut more often than expected.
D.It.s still too early to say whether such a collision might oecur.
What do people think of the suggestion of using nuelear weapons to alter the course of asteroide?
（对应表示比较的信号词：未段第一行中的 worse)
A.It sounds practical but it may not solve the problem.
B.It may create more problems than it might solve.
C. It is a waste of money because a collision of asteroids with Earth is very unlikely.
D.Further research should be done before it is proved applicable.
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