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问题 选择题

如果黄赤交角变大，（  ）

A．五带范围不变

B．热带寒带的范围变大，温带的范围变小

C．热带、寒带的范围变小，温带的范围变大

D．热带、温带的范围不变，寒带消失

答案

答案：B

题目分析：如果黄赤交角的变化导致太阳直射点的位置发生变化，也就是使得南北回归线和南北极圈的纬度数发生变化，黄赤交角的度数等于回归线的度数，黄赤交角变大，则回归线度数变大，有太阳直射的地方就是热带，故热带范围变大，又极圈度数和回归线度数互余，则黄赤交角变大，极圈度数减小，寒带范围增大，热带和寒带增大，则温带范围变小，故本题选B。

单项选择题

从所给的四个选项中，选择最合适的一个填入问号处，使之呈现一定的规律性。（）

A.

B.

C.

D.
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问答题

Man first appeared on the earth about 2 million years ago. Then he was little more than an animal; but early man had a big advantage over the animals. He had in his brain special groups of nerve cells, not present in animals that enabled him to invent a language and use it to communicate with his fellow men. 46) This ability to speak was of great value because it allowed men to share ideas, and to plan together, so that tasks impossible for a single person could be successfully undertaken by intelligent team-work. Speech also enabled ideas to be passed on from generation to generation so that the stock of human knowledge slowly increased.
It was this special ability that put men far ahead of other living creatures in the struggle for existence. 47) He mastered darkness first with dim lights and later with brighter and brighter lamps, until he can now make for himself so dazzling a light with an are lamp that, like the sun, it is too p for his naked eyes.
48) Man found that his own muscles were too weak for the work which he wanted to do; he explored many other forms of power until now he has his hands on the ultimate source of physical energy, the nuclear power. From man’s earliest days the flight of birds has raised his wonder and desire. Why should he not fly as they did Then he began to experiment. At last he learnt how to make the right machines to carry him through the air. Now he can fly faster than sound. Already he has plans for conquering space, and a series of experiments has been completed. 49) It will not be long now before man takes a giant step away from his planet and visits the moon, learning what it is like to have no weight to his body, no upward direction and no downward.
Man, always a wanderer, has to overcome the difficulty of adapting himself to different climates. 50) Fortunately, in spite of having no. thick skin or warm fur to protect him, he is peculiarly p compared with other living creatures, most of whom are unable to live far outside the region that suits them best.
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