Spending 50 minutes with a cell phone close to your ear is enough to change brain cell activity in the part of the brain closest to the antenna (天線). But whether that causes any harm is not clear, scientists at the National Institute of Health said at a conference last month, adding that the study will not likely settle concerns of a link between cell phones and brain cancer. "What we showed is glucose(葡萄糖) metabolism(代謝)(a sign of brain activity) increases in the brain in people who were exposed to a cell phone in the area closest to the antenna," said Dr. Nora Volkow of the NIH, whose study was published in the Journal of the American Medical Associa-tion. The study was meant to examine how the brain reacts to electromagnetic fields caused by wireless phone signals.

　　Volkow said she was surprised that the weak electromagnetic radiation (電磁輻射) from cell phones could affect brain activity, but she said the findings, do not shed any light on whether cell phones cause cancer. "This study does not in any way indicate that. What the study does is to show the human brain is sensitive to electromagnetic radiation from cell phone exposures. " Use of the devices has increased dramatically since they were introduced in the early 1955s, with about 5 billion cell phones now in use worldwide.

　　Some studies have linked cell phone exposure to an increased risk of brain cancers, but a large study by the World Health Organization did not offer a clear answer to this. Volkow' s team stud- ied 47 people who had their brain examined while a cell phone was turned on for 50 minutes and another while the phone was turned off. While there was no complalete change in brain metabolisthey found a 7 percent increase in brain metabolism in the region closest to the cell: phone antenna when the phone was on.

　　Experts said the results were interesting, but urged that they be understood with great care. " Al-though the biological significance, if any, of increased glucose metabolism from too much cell phone exposure is unknown, the results require further investigation," Henry Lai of the University of Wash-ington in the U. S. and Dr. Lennart Hardell of University Hospital in Sweden, wrote in an article in JA-MA. "Much has to be done to further investigate and understand these effects. " They wrote.

　　21. According to the passage, which of the following is TRUE?

　　A. Cell phone use is dangerous.

　　B. Cell phone use causes cancer.

　　C. The human brain is an electromagnetic field.

　　D. There are about 5 billion cell phone users in the world right now.

　　答案：D

　　22. Doctor Volkow was astonished because__________.

　　A. her research has shed light on her understanding of cell phone

　　B. she found that cell phone exposure is harmful to human brain

　　C. she found that using a cell phone for about 50 minutes could influence or change brain activity

　　D. human brain is not responsive to electromagnetic radiation

　　答案：C

　　23. According to the passage, cell phones were launched__________.

　　A. in the late 1970s

　　B. between 1955 and 1960

　　C. in the late 1955s

　　D. in the early 1990s

　　答案：B

　　24. What does the word "that" stand for in the second paragraph?

　　A. Brain activity.

　　B. Her research findings.

　　C. The fact that cell phone use may cause cancer.

　　D. Her research progress.

　　答案：C

　　25. Which of the following is an appropriate tire for this passage?

　　A. Cell Phone Radiation: Is It Harmful?

　　B. Cell Phone Radiation: Is It Useful?

　　C. Cell Phone Radiation: Is It Healthy?

　　D. Cell Phone Radiation: Is It Weak?

　　答案：A

　　Concerning money or anything else, conflicts between husband and wife usually reflect a pow-er struggle. Conflicts between parent and child often centre around the same issue. As children enter adolescence, they begin to demand greater freedom to go where they please, do what they please,and make decisionswithout parental interference. Many American parents do not know how to deal with their teenagers and seek advice from books, lectures, and parent training courses. Parents want to maintain a friendly relationship with their teenagers and also want to guide them so that their be-havior will be whatever the parents consider proper and constructive.

　　But in a society of rapidly changing social and moral values, parents and children often disagree about what is important and what is right.

　　Arguments may concern such unimportant matters as styles of dress or hairdos. But quarrels may also concern school work, after school jobs, decisions, use of the family car, dating, and sex behavior. Some families have serious problems with teenagers who drop out of school, run away from home, or use illegal drugs. Because so much publicity is given to the problem teenager, one gets the impression that all teenagers are troublemakers. Actually, relatively few adolescents do an- ything wrong, and nearly all grow up into "solid citizens" who fulfill most of their parents' expec-tations. In fact, recent studies show that the "generation gap" is narrowing. The vast majority of teenagers share most of their parents' values and ideas. Many parents feel that they get along with their adolescents quite well.

　　26. According to the writer, conflicts between husband and wife usually reflect__________.

　　A. feeling of hatred

　　B. power straggle

　　C. that they don' t care for each other

　　D. that they may appeal to divorce

　　答案：B

　　27. As children enter adolescents, they begin to do the following EXCEPT__________.

　　A. demanding greater freedom to go wherever they please

　　B. making decisions without parental interference

　　C. getting married whenever they please

　　D. doing what they please

　　答案：C

　　28. "...generation gap is narrowing. "means__________.

　　A. the adolescents now become timid

　　B. parents come to get along with their children

　　C. the vast majority of teenagers share most of their parents' values and ideas

　　D. parents and teenager don' t like to quarrel

　　答案：C

　　29. Parents and children often disagree about what is important or right because__________.

　　A. they have different styles of life

　　B. they hate each other

　　C. parents think that their children are troublemakers

　　D. they are in a society of rapidly changing social and moral values

　　答案：D

　　30. When many American parents don' t know how to deal with their children they seek advice from the following EXCEPT__________.

　　A. neighbors

　　B. parent-training courses

　　C. books

　　D. lectures

　　答案：A