8. Which of the following is closest in meaning
to the phrase "leveled off" in the paragraph 2?
A. Reached its lowest level in popularity. B. Stopped being popular.
C. Stopped increasing in popularity. D. Become very
popular.
C
Unless we spend money spotting and preventing asteroids (小行星)
now, one might crash into Earth 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'll have 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 doing so? Two things 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 asteroid big enough to
destroy lots of life might strike Earth once every 500,000 years. Sounds pretty
rare--but if one did fall, it would be the end of the world. "If we don't
take care of these asteroids, they'll 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 sitting around on Earth? "The world
has less to fear from doomsday (世界末日) rocks than from a great nuclear fleet set
against it," said a Nero York Times article.