问题补充：
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.
Brief 1
People living in a particular 2usually have the same skin color and there are many different skin colors in the world.
Reason for skin color
The reasons for different skin colors mainly 3in biology and history.
Biology reasons
The amount of melanin, by which a person’s skin color is 4 , varies from people to people. The more melanin a person has, the 5 his or her skin will be.
Vitamin D is another source 6skin color. Vitamin D is necessary for humans to build bones. Sunlight contributes to vitamin D in the skin.
Historical reasons
The earliest people in Africa hioknj006Dad 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 7 vitamin D, their skin color became lighter.
Generally speaking, people in areas with strong sunlight, have darker skin 8people in other areas have lighter skin.
9
Melanin 10an important role in our skin color. With our living environment changing, melanin production is changed, which leads to the changes in our skin color.
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答案：
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解析：
【小题1】归纳总结题。根据文章第一段内容可知。
【小题2】原词再现。根据第一段第2行living in particular areas。
【小题3】句意转换。根据第一段最后一句Biology and history are the two reasons for this.
【小题4】句型转换。根据第2段第一行…determines a person’s skin color
【小题5】原词再现。根据第2段第2行。
【小题6】词形转换。根据第三段第1行。
【小题7】原词再现。根据第三段第4行。
【小题8】原词再现。根据第四段第五行。
【小题9】归纳总结。通读全文可知这里是得出的最终的结论。
【小题10】固定词组。Play a role in…在…中起作用。
