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  3. Despite the fact that comets are probably the most numerous astronomical bodies in the solar system aside from small meteor frag

Despite the fact that comets are probably the most numerous astronomical bodies in the solar system aside from small meteor frag

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问题     Despite the fact that comets are probably the most numerous astronomical bodies in the solar system aside from small meteor fragments and the asteroids, they are largely a mystery. Scientists do not know exactly what comets are or where they come from. Educated guesses are the best we have in hand.  
    Considering the role of comets in legend and the memory of man, it is remarkable that we still know so little, relatively, about them. The most famous comet of all, Halley’s Comet ( named for the man who predicted its return), was first sighted by the Chinese in 240 B．C．, and it has returned to terrify the people of the world on a regular basis every since then. The ancient considered it an object of ill omen. By mysterious coincidence, the arrival of Halley’s Comet coincided with such events as the battle of Hastings in 1066, the Jewish revolt of 66 A．D．, and the last battle of Attila the Hun against the Romans. Nor is it the only comet to fill man with awe, but merely the most famous in a rich aristocracy of blood-freezers.  
    Comets are even more fascinating to amateur astronomers than to professionals, because this is one area where amateurs can make major discoveries. Comet Ikeya Seki, one of the brightest comets to appear in this century was discovered in 1965 by a pair of Japanese amateurs, Ikeya and Seki. The person who discovers a new comet gets his (or her) name put on it. And amateurs have a head start in the race to discover new comets; the shorter focal lengths on their smaller telescopes give them a positive advantage over the huge telescopes such as Mount Wilson which is built to scan for galaxies, not comparatively short distances.  
    Most scientists tend to agree with astronomer Fred T. Whipple that a comet is really a large mushy snowball of frozen ices and gases ( ammonia, methane, possibly carbon dioxide) with a few bits of solid particles stuck inside. But no one is sure how comets are created in the first place.  
    Scientist believe that comets don’t exhibit their characteristic tail while they lurk fat out in space away from the warmth of the sun but, rather, wander in the form of frozen lumps, like icebergs. This is the core of the comets. Only when the comet approaches the heat of the sun, does the ice begin to melt and stream away in the form of visible gases. The tails of the comets stream out behind for, literally, astronomical distances. Halley Comet had a tail of 94 million miles long when it visited here in 1910．The Great Comet of 1843 had a tail of 186 million miles long.  
Which of the following about comets is INCORRECT?
选项 A、They are great in number.
B、Their arrivals used to frighten human beings.
C、They are named after their discoverers.
D、They are large mushy snowballs of frozen ices and gases.
答案D
解析 由首段首句可以推断A“彗星数量很多”正确；文章第二段曾提及，古人认为彗星是不祥的征兆，哈雷彗星的几次回归都与战争巧合，但它却不是惟一令人类恐惧的彗星，故B与原文意思相符；由第三段倒数第二句谈到“发现新彗星的人都能用自己的名字为其命名”，可以知道C也正确；由倒数第二段可知，“彗星是一团由冰和冰块状的气体(氨，甲烷，可能还有二氧化碳)组成的大大的’脏雪球’”，这是由惠普尔提出的，虽然很多科学家表示赞同，但谁也无法确定，故D是错误的，因此选D。   
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