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2. 今天我有點兒不舒服，不能你一起吃晚飯了。

I'm sick today so that I can’t join you for dinner.

題目來源：2016年英語周報八年級新目標 > 第46期英語周報八年級新目標

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You can tell a lot about people by looking at their hair 一 not just whether they brush,spray,or blow-dry. Scientists have found a way to use hair to figure out where a person is from and where that person has been. The fTnding could help solve crimes among other useful applications.

Water is central to the new technique. The liquid makes up more than half an adult human's body weight. Our bodies break water down into hydrogen (氫) and oxygen. Atoms of these two elements end up in our tissues,fingernails,and hair.

But not all Water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. In the case of hydrogen,for example,there are three types according to their weights. Each type is called a hydrogen isotope (同位素) .And depending on where you live,tap water contains different isotopes.

Can hair record this information? That's what James R. Ehleringer,an environmental chemist at the University of Utah,wondered. To find it out,he and his colleagues collected hair from hair stylists in 65 cities in 18 states across the United States. Even though people drink a lot of bottled water these days,the researchers have found that people's hair has the same isotopes as found in the local tap water. That's probably because- people usually prepare their food with the local water.

Authorities can now use the information to analyze hair samples from criminals,or crime victims and to narrow their search for clues. For example,one hair sample used in Ehleringer's study came from a.man who had moved from San Francisco to Salt Lake City. As his hair grew,it reflected his change in location.

5. What do we know about the hydrogen isotopes,according to Paragraph 3 ?

A. They are classified by^?ize.

B. Each type of them differs in weight.

C. They can improve the quality of tap water.

D. Some of them cannot combine with oxygen.

6. Why is it possible to know where people are from by analyzing their Hkir?

A. People use the same bottled water.

B. People wash their hair in different ways.

C. People's hair is affected by the weather of the places they stay.

D. People's hair indicates the type of water in the places they stay.

7. The last paragraph is mainly to show .

A. how to recognize criminals