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阅读下面短文。完成41~44题。 科学家曾这样想象:如果由带正电的电子与带负电的原子核组成原子,那么

阅读下面短文。完成41~44题。

科学家曾这样想象:如果由带正电的电子与带负电的原子核组成原子,那么就是反原子,反原子则可构成反物质。倘若反物质与物质相遇就会爆炸成光辐射。这一“反物质假说”,在21世纪将逐步变成现实。2002年9月欧洲核子研究中心宣布,世界各地9个研究所的39位科学家通力合作,在受控条件下成功制造了约5万个反氢原子。科学家也在研究过程中发现了正电子,这使他们更相信所有粒子都有其反粒子,从而更有信心揭开反物质之谜。 世界公认的宇宙诞生理论大爆炸学说认为,宇宙是从140亿年前一个“极小的点”爆炸而来的,在那个点之外,“没有时间、没有空间、没有能量、没有物质”,大爆炸产生了大量的正能量和负能量,而总能量仍然为零。能量与物质是可以相互转化的,那么,大量的能量亦应转化为正物质和反物质。这是反物质理论研究的基础。但要想在反物质乃至宇宙诞生理论研究上取得突破,还需要在研究实践中寻求更新的科学思想作指导。 1

40亿年前宇宙诞生时产生了大体相等的物质与反物质。这些反物质在哪里?宇宙存在着由反物质组成的星系,是一种解释;宇宙诞生产生的物质多于反物质,二者相互湮灭后,剩余的物质构成了现在之宇宙,是另一种解释。科学家没有放弃在自然界中寻找反物质的努力,并且成功地在实验室中制造出反物质,以便更直接地研究反物质现象。科学家认为,先进的探测手段在反物质理论研究中不可或缺。 根据伽玛射线探测卫星提供的有关资料,有的科学家认为在银河系上方3500光年处可能存在不断喷射反物质的源头。航天飞机携带的阿尔法磁谱仪升空探测虽未发现反物质,但它最近几年在太空采集的大量数据,对反物质理论研究的突破性进展会有巨大帮助。在自然界寻找反物质的难度甚大,而利用加速器将负离子流射向氙原子核已能制造反氢原子,因此科学家更注重在实验室中进行的反物质研究。

目前在实验室制造反基本粒子并不困难,但将正电子与负原子核结合并能证实它们已成为反原子的工作极为复杂。欧洲核子研究中心耗资1150万美元研制的加速器利用磁场将高能反质子减速为光速1/10的反质子,制造出约5万个低能量状态的反氢原子。

跨过这个里程碑再前进,还需要科学家研制功能更强大的“工具”。 “反物质假说”认为:反物质与物质相遇会释放所有的能量。科学家预测该释放率远远高于氢弹爆炸。航天专家已经对反物质燃料的价值表示神往。科学发现的应用价值是人所关心的。当年一位贵妇人问电的发现者法拉第:“电有什么用呢?”法拉第反问了一句:“新生的婴儿有什么用呢?”关于反物质的应用价值,目前只能作些模糊预测。

41.下列对“反物质假说”内容的叙述,正确的一项是()。

A.宇宙中存在的反物质是由带正电的电子与带负电的原子核结合形成的

B.“反物质假说”不是科学幻想,正电子的发现证实了宇宙中存在反物质

C.如果有反原子构成的反物质存在,它一旦与物质相遇,会释放所有的能量

D.科学家根据宇宙诞生理论想象,宇宙存在由带负电的反原子构成的反物质

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It was already late【41】 we set out f or the next town, which was about fifteen miles away on【42】 side of the town.

There we felt that we【43】 find a bed for the night. It was getting dark【44】 after we left the village, but【45】 we met no one,【46】 we drove fast along the narrow road. As we climbed at times to see the road, I asked John, my friend,【47】 more slowly.

After we had【48】 for about twenty miles, there was【49】 no sign (标志) of the town which was marked【50】 the map. We were beginning to get worried.

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A.if

B.when

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Summer holiday camps (夏令营) for children began in the USA over sixteen years ago. Today there are【41】than 8,000 summer camps in the United States and every year【42】. four million children pass through their gates【43】June and August. Some【44】 by bus every day from the nearest town.【45】 stay as campers for one or two weeks. Quite a lot of children go off to camp【46】the whole of the summer holiday. The people there are young and【47】 There is good food and lots of interesting things【48】. In many camps children learn things【49】cooking and drawing pictures. Every evening there are camp fires and games. Everyone goes to bed【50】but happy.

(41)

A.more

B.many

C.much

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第4题
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I shall always remember my tenth birthday. All my friends came【41】my birthday party.

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A few minutes【46】, my parents brought my birthday cake (蛋糕) with ten candles (蜡烛) on it. I was then asked to cut【47】and the guests were served. Music【48】during the party. The guests were talking and laughing.【49】the party, I thanked my parents【50】holding such a lovely birthday party for me.

(41)

A.to

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Li Lei works in a farm tool factory. He and five of his friends are very interested in singing. So they have (41) a singing group which is called Happy Birds. They sing (42) songs both in Chinese and in foreign languages. They sing very (43) . The other workers and people (44) the villages around really like to hear them (45) . Now New Year's Day (46) here soon. The Happy Birds have been asked to (47) at different places. They'd (48) to go to all of them. (49) one friend has too much work and (50) may have to give up his holidays. The Happy Birds can't sing without him.

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Many students do not like to study history (历史) . They say that there are【41】 many names and dates to【42】 . But if we do not know about the【43】 , we cannot understand the present well. For example, if we wish to know how men【44】 to use fire, we have to know what men did【45】 the past to travel at night or to keep themselves【46】 in cold nights. Only a study of history will make us realize (意识到)【47】 everything we do today is the result of what【48】 people did in the past.

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Indians always shake(摇) their heads when they talk to others. (41) does not have the same meaning (42) "no". If someone wants to visit India, (43) should know this, (44) it will give him some trouble.

One day, a foreign officer went to India on business. He hired(雇佣) a car and an Indian to drive it.When he (45) the driver to send him to his office the driver shook his (46) at once. The officer repeated his order, and the driver (47) so again. At last, the officer, of course, got (48) . “ (49) dare you refuse(拒绝) my order?" he shouted. "Drive me to office immediately!"

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A.It

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Tourism(旅游) was not always as important as it is today.

In the past only wealthy(富有的) people could travel (41) vacations to other countries. More people travel today than in the past (42) there is a growing middle class in many parts of the world. People now (43) more money for travel. Special airplane fares for tourists make travel (44) expensive and thus more attractive(有吸引务的) than (45) before.

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A.on

B.with

C.to

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Four girls went to school every day【41】 taxi.

One day one of the girls said, "There is a test this morning. Let's get to school【42】. Then we won't have to take the【43】."

"What can we tell the teacher?" one of the girls said. "He'll be【44】. We'll need a good【45】."

The girls thought for several moments, then one of them said, "Let's【46】 him that our taxi had a flat tire (轮胎气) "

"That's a good idea," the other girls said. "We'll tell him that." They【47】 at school an hour later. The test was finished.

"Why are you late?" the teacher asked. "You【48】 the test."

"Our taxi had a flat tire," one of the girls said.

The teacher thought for a moment, then he said, "Sit down, one of you in each【49】 of the room."

The four girls did this.

Then the teacher said, "Write on a piece of paper the【50】 to this question: Which tire was flat?"

(41)

A.in

B.on

C.by

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