题目内容
E
Could we "terraform" Mars —that is, change its frozen, thin-aired surface into something more friendly and Earthlike? Should we? The first question has a clear answer: Yes, we probably could．Spacecraft, including the ones now exploring Mars, have found evidence that it was warm in its youth, with rivers flowing into vast seas．And right here on Earth, we've learned how to warm a planet: just add greenhouse gases to its atmosphere．Much of the CO2 that once warmed Mars is probably still there, in frozen dirt and polar ice caps, and so is the water．
Most of the work in terraforming, says NASA scientist Chris Mackay, would be done by life itself． "You don't build Mars," Mackay says．"You just warm it up and throw some seeds．" Powerful greenhouse gases could be produced from elements in dirt and air on Mars and blown into the atmosphere; by warming the planet, they would release the frozen CO2, which would quicken the warming and increase atmospheric pressure to the point where liquid water could flow．Meanwhile, says botanist James Graham of the University of Wisconsin, human settlers could seed the red rock with a succession （系列） of ecosystems ?first bacteria and lichens （地衣）, which survive in Antarctica, later mosses （苔藓）, and after one thousand years or so, redwoods．Getting breathable oxygen levels out of those forests, though, could take thousands of years．
However, Mars is in no immediate danger．Some space scientists recently recommended going to the moon or an asteroid （小行星） first, and pointed out the space agency lacks the funds to go anywhere．It didn't estimate the cost of gardening a dead planet．
72．What is the most essential to make Mars fit for living?
A．Turn ice into flowing water． B．Clean the dirty atmosphere．
C．Make the atmosphere more suitable． D．Go to the moon or an asteroid first．
73．What does the author think of the idea ofterraforming Mars?
A．We could do it． B．We couldn't do it．
C．We should do it． D．We shouldn't do it．
74．In the botanist's opinion, man needs to __________.
A．enable Mars to clean its atmosphere
B．build a greenhouse on Mars
C．send some people to settle on Mars
D．cultivate ecosystems from lower to higher life form
75．What is the best title for the passage?
A．Making Mars the New Earth． B．A Good Way to Change the Universe
C．Humans' Great Power． D．Terrible Science and Technology．
72-75 CADA
解析
天天向上一本好卷系列答案
小学生10分钟应用题系列答案
Do you know Australia? Australia is the largest island in the world. It is a little smaller than China. It is in the south of the earth. 1 The population of Australia is nearly as large as that of Shanghai. 2 The cities in Australia have got little air or water pollution. The sky is blue and the water is clean. You can
clearly see fish swimming in the rivers. Plants grow very well.
Last month we visited Perth, the biggest city in western Australia, and went to a wild flowers’ exhibition 3 We had a wonderful time. Perth is famous for its beautiful wild flowers. In spring every year Perth has the wild flowers’ exhibition.
After visiting Perth, we spent the day in the countryside. We sat down and had a rest near a path at the foot of a hill. It was quiet and we enjoyed ourselves. Suddenly we heard bells ringing at the top of the hill. 4 There were about three hundred sheep coming towards us down the path. 5 After a short drive from any town, you will find yourself in the middle of white sheep. Sheep, sheep, everywhere are sheep.
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A．The government has made enough laws to fight pollution. |
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B．Australia is the sixth largest country in the world. |
C．Australia is famous for its sheep and kangaroos. |
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D．Australia is big, but its population is not large. |
E. What we saw made us pick up all our things and run back to the car as quickly as we could.
F. There we saw a large number of wild flowers we had never seen before.
G. The people of Australia are very hardworking.