Unluckily.when I dropped in.Doctor Li for Beijing to attend an important conference.so we only had time for a few words．( )A．just leftB．has just leftC．is just leavingD．was just leaving 题目和参考答案——青夏教育精英家教网—

16．Of all the problems facing modern astronomers，perhaps the most fascinating is："Can intelligent（有智能的） life exist elsewhere？"Since the Earth is an unimportant planet moving round an unimportant star，it would be a pride on our part to suppose that we are the only intelligent beings in the universe．But to obtain proof is difficult．
The main trouble is that our neighbor worlds，the bodies in the solar system appear to be unsuitable for advanced life forms．The Moon may be ruled out at once； it has hardly any atmosphere．Venus（金星） is little better； the surface temperature is extremely high and the atmosphere is mostly carbon dioxide．Mars（火星） with a very thin atmosphere and a severe shortage of water，may well support simple plant life but there seems no hope of finding animals，while the attractive Martians of the story-tellers have long since been given up．
Of course this has not stopped the flow of bright ideas for communicating with the supposed people on Mars．In the early nineteenth century the great mathematician Gauss suggested planting tree-patterns in Siberia，so that the Martians would see them and replay suitably．Following up this idea，the Austrian scientist Karl Littrow proposed digging very wide ditches（沟） in the Sahara，triangular in patterns，and then filling them with petrol or some substance so that，when lit，the ditches would present Martian observers with a"flaming triangle"which would show the existence here of intelligent minds．Even better were the plans of Charles Cross，a French writer of the 1870's，who wanted to build a large mirror to reflect the sun's rays and concentrate them on the surface of Mars，thereby making a vast burning-glass．By swinging the mirror around，Cross explained it would be practicable to write words in the Martian deserts simply by burning the sand．For many years he bombarded （鼓吹） the French government with literature about this plan and was very disappointed when no official interest was shown．

48．From the passage we can learn that the opinion of the writer is thatC．
A．people on the earth are almost certainly the only intelligent beings in the universe
B．people on the earth are definitely the only intelligent beings in the universe
C．there may be other intelligent beings in the universe
D．there are other intelligent beings in the universe
49．Why is there unlikely any life on Venus？D
A．Because the weather is too cold．
B．Because it is severely short of water．
C．Because it has a very thin atmosphere．
D．Because the surface temperature is too hot．
50．According to the passage，it seems that MarsC．
A．may have both vegetable and animal life
B．may be inhabited by attractive Martians
C．may have some vegetable life
D．can have no life at all
51．How did Gauss，the mathematician，want to establish contact with the Martians？B
A．By building a large mirror．
B．By making patters with trees．
C．By filling wide ditches with oil．
D．By planting trees in triangular shape．
52．It can be learned from the last paragraph that Charles Cross feltA．
A．disappointed at the lack of official interest shown in his plan
B．surprised that the officials were interested in his suggestion
C．angry when the government paid little attention to his ideas
D．pleased when the government did take notice of his plan．

18．Shortly after publication，the book became ____ because of the writer's repeated use of the negative word"nigger"to refer to the black Americans．（　　）

A．

universal

15．Their money was used up and they had to give up the project．（将并列句改为简单句）

6．Do you know what subjects they major in while they were at college？major改为majored．

	A．	just left		B．	has just left
	C．	is just leaving		D．	was just leaving

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