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1、(1)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(决定) a persons skin color. The more melan
2、in 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 persons body will produce less melanin, making the skin lighter.Skin
3、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(吸收) by melanin cannot be used for vitamin D production. Therefore, a darkskinned person will produce less vi
4、tamin D than a lightskinned 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(进化). The earliest humans lived in Africa, their dark skin produced less vitamin D because of their dark skin. As a result,
5、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(例外) to this i
6、s 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
7、 have lived. This has in turn changed our melanin production, and eventually, skin color. Brief 1._People living in a particular 2._ usually have the same skin color and there are many different skin colors in the world.Reason for skin colorThe reasons for different skin colors mainly 3._ in biology
8、 and history.Biology reasonsThe amount of melanin, by which a persons 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 6._skin color. Vitamin D is necessary for humans to build bones. Sunlight contributes to v
9、itamin D in the skin.Historical reasonsThe 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 7._ vitamin D, their skin color became lighter.Generally speaking, people in areas with s
10、trong sunlight, have darker skin 8._ people in other areas have lighter skin.9._Melanin 10._ 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.Introduction, area, lie , determined, darker, affecting,
11、 produce, while, Conclusion, plays(2)It is said that English speakers fall into three groups: those who have learnt it as a mother tongue, those who have learnt it as a second language through exposure(显露) in a society where it is spoken, and those who are forced to use it for administrative(管理的), p
12、rofessional or educational purposes. This third group, along with the supremacy(至高地位) of English in the business world, has created a fast development in institutions(机构) offering English for business. However, the average business person, while happily accepting the challenge, does not have any ide
13、a how long the process may take. Duncan Ford, a specialist in language teaching theory, partly puts the blame on misleading publicity and says that you have to think in terms of hundreds of hours while people still think learning a language is a three-hour-a-week job. According to him, the key is lo
14、ts of variety of the activities similar to the happiness of the class. The communicative way has replaced the oldfashioned note-taking method and for those people who think that a couple of hours with the latest CD-ROM is not to replace English classes, and they should think again. While seen as a u
15、seful back-up, they are not teacher replacement.Learning English for a Special PurposeClassification() ofEnglish speakersEnglish speakers are 1_up of three groups, those who have learnt it as a mother 2_; those who have learnt it as a second language in society, and those who are forced to use it for a special 3_.The present situation of English for the businessEven though the third group has made institutions which offer English for business 4_ fast, the average business people dont 5_how long the process may take.6_given by a specialistIt takes long to learn Englishhundred
