下列叙述中不属于隋朝灭亡原因的是( ) A.多次发动对外战争 B.残暴的统治 C.大兴土木工程 D.国家财政困难,军费不足 答案:D 点拨:D项与历史实际不符,符合题意。Sixty-five million years ago, an asteroid (小行星) that crashed on Earth led to the disappearance of
the largest animals that have ever walked our planet – the dinosaurs. At least,
this is what some scientists believe. But that accident happened so long ago.
People have come to believe that we are free of threats from asteroids and
everything else from space.
However, what happened on Feb 15 , 2013 was a reminder
that we’re just as vulnerable as the dinosaurs once were. Two objects
from space – a meteor (陨石) and an asteroid called 2012 DA14 –
visited Earth’s atmosphere on the same day. The former fell in Russia, injuring
1,200 people, while the latter passed by Earth at a record-setting close
distance.
Scientists had been expecting the asteroid since last
year, but the meteor was a surprise. NASA’s telescope system only detects
asteroids at least 50 meters in diameter (直径), which is
just about the size of 2012 DA14. But the meteor was much smaller, which made
it harder to spot.
But what if we do spot an asteroid that is headed
right for Earth? There are several possible ways in which dangerous asteroids
could be made to change its orbit. Which method is best depends on several
factors and most importantly – how much time we have to stop it.
If there is enough time before the hit, we can send
off a heavy spacecraft to travel alongside the asteroid. The gravity from the
spacecraft would gradually change the rock’s orbit. Besides that, scientists
could one day use sun-powered lasers to either make asteroids disappear or
change their course. If there’s not enough time, we’ll have to go after the
asteroid with a spacecraft and change its orbit with a crash. Finally, if
things are truly desperate, there will be only one choice left – to use a
nuclear bomb. That could turn the asteroid into a meteor shower, which would be
even more dangerous.
1.The
author mentioned the asteroid that led to the dinosaurs’ dying out to ______.
A. show that asteroids fall from space frequently
B. alert people about the possible danger of objects
falling from space
C. inform readers about the constant threats the Earth
faces
D. suggest that there are still many mysteries about
the universe
2.The
underlined word “vulnerable” in the second paragraph probably means ______.
A. unprotected B.
lonely C. stupid D.
self-important
3.Which
of the following statements is TRUE about the meteor that fell to the Earth in
Russia?
A. It passed by the Earth at a close distance.
B. It was spotted by NASA’s telescope system a year
ago.
C. It is about the same size as the asteroid that
passed by the Earth.
D. It fell to the Earth and caused great damage to the
local community.
4.What
is the main idea of the article?
A. Learning about asteroids and meteors.
B. The threats of objects from space and possible
solutions.
C. NASA’s latest technology to discover visitors to
the Earth from space.
D. How to measure the damage of collisions from
asteroids and meteors.