第四部分 阅读理解（共六篇）
第六篇
Hair Detectives
Water is central to the new technique. Our bodies break water down into its parts: hydrogen and oxygen. Atoms of these two elements end up in our tissues and hair.
But not all water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. Different forms of a single element are called isotopes. And depending on where you live, tap Water1 contains unique proportions of the heavier and lighter isotopes of hydrogen and oxygen.
Might hair record these watery quirks2? That's what James R. Ehleringer, an environmental scientist at the University of Utah in Salt Lake City3, wondered.
To find out, he and his colleagues collected hair from barbers and hair stylists in 65 cities in 18 states across the United States. The researchers assumed that the hair they collected came from people who lived in the area.
Even though people drink a lot of bottled water these days, the scientists found that hair overwhelmingly reflected the concentrations4of hydrogen and oxygen isotopes in local tap water. That's probably because people usually cook their food in the local water. What's more, most of the other liquids people drink including milk and soft drinks contain large amounts of water that also come from sources within their region.
Scientists already knew how the composition of water varies throughout the country. Ehleringer and colleagues combined that information with their results to predict the composition of hair in people from different regions. One hair sample used in Ehleringer's study came from a man who had recently moved from Beijing, China, to Salt Lake City. As his hair grew, it reflected his change in location.
The new technique can't point to exactly where a person is from, because similar types of water appear in different regions that span a broad area. But authorities can now use the information to analyze hair samples from criminals or crime victims and narrow their search for clues.
词汇：
hydrogen n. 氢 overwhelmingly adv. 压倒性
Atom n. 原子 Isotope n. 同位素
span v. 跨越 Quirk n. 古怪举动；怪僻
clue n. 线索 Stylist n. 发型师
注释：
1. tap water: 自来水，管道供水
2. watery quirks: 水的奇特性质。quirk的含义是“an peculiar or unexpected behavioral habit”(古怪的不可预测的行为和事情)。
3. University of Utah in Salt Lake City: (美国)盐湖城的犹他大学
4. concentrations: 浓度；含量
练习:
1. What does the writer say about tap water? Which of the following is NOT correct?
A) Tap water reflects the concentrations of hydrogen and oxygen isotopes in different regions.
B) Tap water is a kind of soft drink in the United States.
C) Tap water contains unique proportions of isotopes of hydrogen and oxygen.
D) Tap water is used to cook food.
2. James R. Ehleringer tried to find out
A) if our bodies break water down into its parts.
B) if it is possible to collect hair samples across the country.
C) if tap water contains unique proportions of isotopes of hydrogen and oxygen.
D) if the composition of hair can indicate exactly where people are from.
3. Which of the following statements is meant by the writer?
A) Ehleringer was successful in his research.
B) Ehleringer failed in his research.
C) Ehleringer can be a successful detective.
D) Ehleringer's research proved successful in China.
4. What does the last paragraph tell you?
A) The new technique can tell precisely where a person lives.
B) Water supplied in different regions all come from the same source.
C) Types of water used in different regions provide useful information for the police.
D) Hair samples provide the most important clues to identify crimes.
5. Which of the following is closest in meaning to the title?
A) Human hair may help detectives to solve crimes.
B) Animal hair may help detectives to solve crimes.
C) Detectives watch hairy criminals closely.
D) Most detectives are hair specialists.
答案与题解：
1．B第三段和第六段谈到tap water。A、C、D均是文中提到的内容。8是错误的，因为文章第六段说，我们饮用的牛奶和软饮料都含有大量水分，而没有说tap water是软饮料。
2．C第四段的问句针对第三段的内容。these watery quirks指的是上段中的unique
proportions of the heavier and lighter isotopes of hydrogen and oxygen。所以C是正确答案。
3．A第六段和第七段提供了答案。科学家发现头发能反映出当地自来水中氢、氧同位素的含量；科学家也已经研究出不同地区水成分是不同的，并且在此基础上来确定来自不同地区的人的头发成分。
4．C选项A、B、D与原文均有出入。尽管在一个较大的范围内，人们使用成分较为相同的水，但是水的成分组成提供的信息可以帮助官方缩小破案线索范围。
5．A题目的意思是：人的头发可以帮助侦探破案。
