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  3. 共用题干 Rainmaking1 The idea of rainmaking is almost as old as man,but it was n...

共用题干 Rainmaking1 The idea of rainmaking is almost as old as man,but it was n...

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问题 共用题干
Rainmaking

1 The idea of rainmaking is almost as old as man,but it was not until 1946 that man succeeded in
making rain.In ancient times,rainmakers had claimed to bring rain by many methods:dancing,singing,
killing animals(including humans).
2 For a long time,men have understood where rain comes from.Water from the surface of oceans and
lakes becomes part of the air,where it forms clouds from which rain falls.But exactly what starts the forma-
tion of raindrops was not known until quite recently.A man named John Aitken proved that drops of water
gather around tiny bits of dust or other matter. The centers of the drops are so small that the human eye can-
not see them.Without such centers,it seems raindrops do not form.
3 During World War Ⅱ,Dr. Irving Langmir,and his assistant Schaefer,were hired by the General
Electric Company to study how and why ice forms on the wings of airplanes.They went to a mountain in New
Hampshire,where snowstorms are common and cold winds blow. They were surprised to find that often the
temperature of the clouds surrounding them was far below the freezing point,and yet ice did not form in the
clouds.
4 After the War,Schaefer experimented with a machine that created cold,moist air similar to the air
found in clouds.To imitate the moist air of a cloud.Schaefer would breathe into the machine.Then he
would drop into the freezer a bit of powder,sugar,or some other substance.For weeks and months he tried
everything he could imagine.Nothing happened.No crystals of ice were formed.None of the substances
would serve as the center of a snow crystal or raindrops.
5 One July morning,Schaefer was dropping in bits of various substances and watching the unsuccessful
results.Finally,a friend suggested that they go to eat lunch and Schaefer went with him.As usual,he left
the cover of the freezer up,since cold air sinks and would not escape from the box.
6 Returning from lunch,Schaefer found that the temperature of the freezer had risen to a point higher
than that required for ice crystals to remain solid.There were two choices now.He could close the cover and
wait for the freezer itself to lower the air temperature,or he could make the process occur faster by adding dry
ice a gas in solid form that is very,very cold.He chose the latter plan.As he dropped the steaming white
dry ice into the freezer,he happened to breathe out a large amount of air. And there,before his eyes,it
happened ! He had made ice crystals,not by adding centers to the moisture,but by cooling the breath so
much that the liquid had to form crystals!Then he began to blow his breath into the freezer and drop large
pieces of dry ice through it to create crystals which became a tiny snowstorm falling slowly to the floor of his
laboratory.
7 After planning carefully,Schaefer made an experiment by dropping dry ice from his plane to the
clouds below him.As was expected,snow formed and fell from the bottom of the cloud.Schaefer succeeded.
He made history.
选项 Paragraph 4__________
A:Langmir and Schaefer's Work for the GE Company
B:Langmir and Schaefer's Discovery of Rain-forming
C:Men'S Knowledge of Rain-forming
D:Schaefer'S Several Unsuccessful Experiments
E:Schaefer's Discovery by Accident
F: Langmir and Schaefer'S Successful Cooperation
答案D
解析本段简略地叙述了雨水的来源和形成雨滴的核心部分。
本段介绍了Langmir和Schaefer受雇于通用电气公司（General Electric Company)，研究 机翼结冰的成因。
本段描述了Schaefer从事的人工制造冰晶体的实验，但没有成功。
由文章第六段“As he dropped the steaming white dry ice into the freezer, he happened to breathe out。large amount of air"，可知一次偶然的机会，Schaefer在投人干冰的时候，呼出一大 口气，结果冰晶体却出现了。他在无意中发现了制造冰晶体的方法。
在文章第一段中提到“In ancient times, rainmakers had claimed to bring rain by many methods: dancing, singing, killing animals (including humans)"。该句中提到的作为造雨、求雨 的手段的dancing, singing, killing animals (including humans）等都是不科学的方法。
答题的解释请参阅第26题的说明。
由文章第七段“After planning carefully, Schaefer made an experiment by dropping dry ice from his plane to the clouds below him.As was expected,snow formed and fell from the bottom of the cloud.Schaefer succeeded"，可知选C。
由文章第二段“But exactly what starts the formation of raindrops was not known until quite recently"，可知选B。第4部分：阅读理解第一篇 本篇文章主要讲述了食用土豆对人体免疫系统的益处。
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