题目内容
B. less than
C. more than
D. no more than
One of the most remarkable things about the human mind is our ability to imagine the future. In our 1._____we can see what has not yet happened. For example, while we are looking forward to 2._____a new place or country, we 3._____what it will be like. We predict( 预料) the 4._____ people will eat, dress and act. Of course, we do not always predict things 5._____. Things are often very different from the way we 6._____them to be. One of the 7._____ dreams in history is the dream of the German scientist, Kekule, who had been 8._____ to work out a very difficult problem in physics. He had 9._____and analysed(分析) the problem from every angle(角度) for days, but there 10._____ to be no way of 11._____ out the answer. Then one night he went to bed and dreamed. When he 12._____ up, he realized that he knew the answer. He had solved the problem in his 13._____. The hypnotist(催眠者)sat in the chair opposite him and spoke 14._____: I want you to concentrate on my voice. Think about 15._____. You know nothing but my voice. And as you pay attention to my voice, your 16._____ will get heavier. Soon you’ll be asleep. You will hear my voice and 17._____ my words, but your body will be asleep, your eyes are too heavy. You are 18._____ asleep, and when you wake up you will 19._____ nothing. You will forget everything. Now I am going to 20._____ slowly from one to five. One, two, three, four, five.
1.A.brains | B. senses | C. minds | D. sights |
2.A.visiting | B. seeking | C. reaching | D. discovering |
3.A.imagine | B. know | C. feel | D. guess |
4.A.custom | B. habit | C. style | D. way |
5.A.quickly | B. simply | C. correctly | D. neatly |
6.A.required | B. wished | C. left | D. expected |
7.A.funny | B. dull | C. famous | D. silly |
8.A.managing | B. trying | C. thinking | D. hoping |
9.A.studied | B. learned | C. discussed | D. researched |
10.A.used | B. ought | C. seemed | D. had |
11.A. making | B. finding | C. turning | D. letting |
12.A.gave | B. sat | C. woke | D. got |
13.A.dream | B. lesson | C. research | D. exercise |
14.A.softly | B. loudly | C. slowly | D. firmly |
15.A.everything | B. something | C. nothing | D. anything |
16.A.eyes | B. feet | C. head | D. body |
17.A.believe | B. repeat | C. take | D. understand |
18.A.really | B. extremely | C. actually | D. almost |
19.A.accept | B. remember | C. hear | D. receive |
20.A.count | B. say | C. add | D. Speak |
Have you ever wondered why there are so many skin colors in the world? Do you know why people living in particular areas usually have a certain color? Biology and history are the two reasons for this.
Skin contains something called melanin, which determines a person’s skin color. The more melanin a person has, the darker his or her skin will be. The amount of and the production of melanin are controlled by genetics, but can be affected by other things, such as sunlight. If a person lives in a place with less sunlight, a person’s body will produce less melanin, making the skin lighter.
Skin color is also affected by another source ---- vitamin D. humans all need vitamin D to build bones. People can get it by eating foods such as fish and milk, or from sunlight, so sunlight absorbed by melanin cannot be used for vitamin D production. Therefore, a dark—skinned person will produce less vitamin D than a light—skinned person when they received the same amount of sunlight.
The connection between vitamin D production and skin color is clear when we look at evolution. The earliest humans lived in Africa, their dark skin produced less vitamin D because of their dark skin. As a result, their skin made less melanin, so they could get enough sunlight to produce vitamin D. their skin gradually got lighter and they lost hair. Now, people living in areas with strong sunlight like Africa, have darker skin, while people living in other areas have lighter skin. The exception to this is the Inuit, who live in a place with little sunlight, but have dark skin because they eat a lot of fish and have enough vitamin D.
Evolution has given us a rainbow of skin colors. Humans have always had melanin to determine our skin color. What has changed through history is the environment where we have lived. This has in turn changed our melanin production, and eventually, skin color.
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Brief __71__ |
People living in a particular __72__ usually have the same skin color and there are many different skin colors in the world. |
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Reason for skin color |
The reasons for different skin colors mainly__73__ in biology and history. |
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Biology reasons |
The amount of melanin, by which a person’s skin color is__74__ , varies from people to people. The more melanin a person has, the __75__ his or her skin will be. Vitamin D is another source__76__ skin color. Vitamin D is necessary for humans to build bones. Sunlight contributes to vitamin D in the skin. |
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Historical reasons |
The earliest people in Africa had dark skin with hair covering it because the sunlight is very strong. When they moved to places where they could not get enough sunlight to__77__ vitamin D, their skin color became lighter. Generally speaking, people in areas with strong sunlight, have darker skin __78__ people in other areas have lighter skin. |
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__79__ |
Melanin__80__an important role in our skin color. With our living environment changing, melanin production is changed, which leads to the changes in our skin color. |