题目列表(包括答案和解析)
A few weeks ago, an asteroid (小行星) almost 30 feet across and flying along at 38,000 miles per hour
flew 28,000 miles above Singapore. Why, you might reasonably ask, should we care about a near miss from
such a tiny rock? Well, I can give you one very good reason: asteroids don't always miss. If even a relatively
little object was to strike a city, millions of people could be wiped out.
Thanks to telescopes that can see ever smaller objects at ever greater distances, we can now predict
dangerous asteroid impacts decades ahead of time. We can even use current space technology and fairly
simple spacecraft to alter an asteroid's orbit enough to avoid a collision. We simply need to get this detection-
and-deflection program up and running.
President Obama has already announced a goal of landing astronauts on an asteroid by 2025 as a pioneer
to a human mission to Mars. Asteroids are deep-space bodies, orbiting the Sun, not the Earth, and traveling
to one would mean sending humans into solar orbit for the very first time. Facing those challenges of radiation,
navigation and life support on a months-long trip millions of miles from home would be a perfect learning
journey before a Mars trip.
Near-Earth objects like asteroids and comets-mineral-rich bodies bathed in a continuous flood of sunlight-
may also be the ultimate resource depots for the human being.
To be fair, no one has ever seen the sort of impact that would destroy a city. The most instructive incident
took place in 1908 in the remote Tunguska region of Siberia, when a 120-foot-diameter asteroid exploded
early one morning. It probably killed nothing except reindeer (驯鹿) but it flattened 800 square miles of forest.
Statistically, that kind of event occurs every 200 to 300 years.
Luckily, larger asteroids are even fewer and farther between-but think of the asteroid seven to eight miles
across that annihilated the dinosaurs (and 75 percent of all species) 65 million years ago.
Certainly, when it comes to the far more numerous Tunguska- sized objects, to date we think we've
discovered less than a half of I percent of the million or so that cross Earth's orbit every year. We need to
pinpoint (定位) many more of these objects and, predict whether they will hit us before it's too late. With a
readily achievable detection-and-deflection system we can avoid the dinosaurs' fate.
It’s reported that the fire that ______ at two o’clock last night caused a lot of damage.
A. breaking out B. breaks out C. broke out D. was broken out
It’s said that the food supplies in that flood-stricken area have __________ and what is worse, the patience of the poor people there is _______.
A.run out; using up | B.been run out; used up |
C.been used up; running out | D.used up; being run out |
Animals Can Sense Natural Disasters
Among the dead in South Asia’ s tsunami(海啸)were many tourists at Sri Lanka’ s national wildlife park at Yala. But very few of the park’s animals — elephants, buffaloes, monkeys and wild cats — appear to have died. There are theories that animals can sense natural disasters and run away to safety.
First, it’s possible that the animals may have heard the quake before the tsunami hit. The underwater burst produced sound waves known as infrasound(次声). Humans can’t hear infrasound, but many animals including dogs, elephants, tigers and pigeons can.
A second early warning sign the animals might have sensed is ground vibration(震动). The great quake would have produced vibrational waves known as Rayleigh waves. These vibrations move through the ground like waves moving on the surface of the ocean but faster. They travel at ten times the speed of sound. The Rayleigh waves would have reached Sri Lanka hours before the water hit. Mammals, birds, insects and spiders can sense Rayleigh waves. So the animals at Yala might have felt the Rayleigh waves and then run to higher ground.
But what about humans? While we can’t hear infrasound, we can feel it, although we don’t necessarily know we’re feeling it. We also experience Rayleigh waves by special sensors in our joints(关节), which exist just for that purpose. Sadly, it seems we don’t pay attention to the information when we get it. Maybe we screen it out because there’s so much going on before our eyes and in our ears.
1.Why did few animals at Yala die when the tsunamis that caused a huge number of human deaths hit?
A.Because human beings cannot hear the infrasonic sound.
B.Because the animals were staying at a higher place in the park.
C.Because the animals were able to run much faster than human beings.
D.Because the animals might have picked up the danger signals and ran away.
2.Which of the statements about “Rayleigh waves” is true?
A.Rayleigh waves can be felt both by animals and human beings.
B.Rayleigh waves, just like infrasonic sound, can only be felt by animals.
C.Rayleigh waves are vibrational waves that usually cause quakes or tsunamis.
D.Rayleigh waves move on the ocean surface at a speed ten times that of sound waves.
3.According to the passage, which of the statement is true?
A.We can’t feel the infrasound so we can’t be informed of the danger.
B.We ignore the information of tsunami’s coming even though we can also get it.
C.We were so busy on our minds that we feel neither infrasound nor Rayleigh waves.
D.We can feel Rayleigh waves and infrasound so we can escape the danger like animals.
It’s required that the students___ mobile phones in their school, so seldom ____ them using one.
A. not use; will you see B. should not use; you will see
C. don’t use; will you see D. would not use; you will see
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