题目内容

________ with a gas which is lighter than air, a balloon can float in the air.

A.
When filling
B.
When filled
C.
Filling
D.
Having filled

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阅读下列短文, 从所给的四个选项中, 选出最佳答案。　　　　

　　 Milan, the second largest city of Italy, has won an undesirable　　 (不受欢迎的) world record. Of the 54 big cities studied by the World　　 Health Organization and the United Nations, Milan was considered to　　 have the worst air pollution.　　

　　 According to these two 10-year studies, the level of air pollution　　 in Milan is twice as high as the levels in Paris and Beijing and three　　 times those in Tokyo and London, and four times that in New York.

　　 The reason for Milan's bad pollution, according to the scientists,　　 is that the city is situated in a valley that holds back the poisonous　　 gases.

　　 Though Milan has taken some measures to lower the level of　　 pollution, the situation is still worrying. People joke about each　　 other, "If you're travelling to Milan, be sure to bring your gas mask."　　　　

(1) Which is not mentioned in the passage?

[ ]

A. The reason for the air pollution in Milan.　　

B. The measures taken by Milan to solve the problem.

C. The city's air regarded to be worst polluted.

D. The conclusion that the air in Milan was badly polluted.　　

(2) Which of the following correctly shows the level of air pollution

in Milan?

[ ]

　　 A. 　　　　B. 　　

C. 　　 D.

(3) Why is the air pollution in Milan so serious?

[ ]

A. Because the city lies in a place where it is difficult for polluted air to move away.

B. Because too many cars are being driven in the city.

C. Because the city has some mountains.

D. Because Milan has taken some worrying measures.

(4) This passage tells us __________.

[ ]

A. it is quite easy to breathe the air in Milan 　　

B. it is dangerous to breathe the air in Milan 　　

C. it is impossible to travel in Milan without a gas mask 　　

D. it is funny to travel in Milan with a gas mask

______ with a gas lighter than air, a balloon can float in the air．

[　　]

A．When filled 　　　B．Filling

C．Having filled 　　D．When filling

Reading Comprehension

　　Men always wanted to fly．For hundreds of years they watched birds flying and wished that they could fly too．Birds fly very easily．They beat the air with their wings and climb up through the air．The air keeps them up．

　　Men knew how to make kites hundreds of years ago．Kites could stay in the air for many hours．“If birds and kites stay up in the air, perhaps we can,” they thought．

　　At first they made wings like birds．Then they jumped off high buildings and tried to fly．Many men did this but they failed to fly．They crashed to the ground．Some were killed and some were badly hurt．After many times they stopped trying to fly with wings．Then two brothers tried another way．They tried balloons．“Hot air is lighter than cold air,” they said．“That is why hot air goes upwards．If we fill a balloon with hot air it will go upwards．”

　　They built a balloon．It was made of thin cloth and paper．They lit a fire beneath it．Up into the air it went! It reached a height of 1, 800 meters．Then the air inside the balloon became cool and it slowly downed and gently rested on the ground．

　　A few months later the brother sent up another balloon．This time there was a basket hanging underneath it．In the basket there were three animals： a sheep, a duck and a hen．The balloon traveled through the air to a place two and half kilometers away．Then it came down safely to earth．Now it was time for men to fly! In October 1783 another of the brothers’ balloons went up．This time a man went with it．The balloon did not rise very far．It went, only to twenty－five meter．It was tied to the ground by a rope．A month later two men went up in a balloon full of hot air．This time there was no rope! A great crowd of people watched．The balloon rose to a height of 900 meters．The wind blew it along for nine kilometers．Then it came gently back to earth．Men had traveled through the air for the first time．

　　Other men filled the balloon with a gas called hydrogen．Hydrogen is much lighter than air．Balloon filled with it were able to travel long distances．But the men in the basket underneath could not steer them．They went where the wind took them．

　　Later balloons were made in the shape of a cigar．These were called airships．They had engines to drive them alone, and they could be steered a little．But they were still blown about by the wind．The hydrogen gas was dangerous, too．It caught fire very easily．There were many accidents and many people died．At last they stopped making airships．

(1)

When some men tried to fly with wings, ________．
[　　]
A．	a few of them succeeded
B．	none of them succeeded
C．	many of them succeeded
D．	all of them succeeded

(2)

The first balloon were filled with ________．
[　　]
A．	hot air
B．	hydrogen
C．	cold air
D．	feathers

(3)

Balloons were not a good way to travel because they ________．
[　　]
A．	went too high
B．	went too low
C．	had to be tied to the ground by a rope
D．	could not be steered

(4)

Hydrogen was not a good gas for airships because it ________．
[　　]
A．	was the wrong shape
B．	was too heavy
C．	was too light
D．	caught fire easily

1. When filled with a gas lighter than air,a balloon can_____in the air. A.fly　 B.float　 C.wander　 D.sail

________ with a gas which is lighter than air, a balloon can float in the air.

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