【正文】 90.The forest environment processed and redistributed the lead faster than the scientists had expected. Scientists say both studies demonstrate that certain parts of the ecosystem (生態(tài)系統(tǒng) ) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used asa license to pollute.21. The study published in the journal Nature indicates that A) the Clean Air Act has not produced the desired resultsB) lead deposits in arctic snow are on the increaseC) lead will stay in soil and snow longer than expectedD) the US is the major source of lead pollution in arctic snow22. Lead accumulation worldwide decreased significantly after the use of unleaded gas in the US A) was discouragedB) was enforced by lawC) was prohibited by lawD) was introduced23. How did scientists discover the source of lead pollution in Greenland?A) By analyzing the data published in journals like Nature and Ambio.B) By observing the lead accumulations in different parts of the arctic area.C) By studying the chemical elements of soil and snow in Northeastern America.D) By paring the chemical positions of leaded gasoline used in various countries.24. The authors of the Ambio study have found that A) forests get rid of lead pollution faster than expectedB) lead accumulations in forests are more difficult to deal withC) lead deposits are widely distributed in the forests of the USD) the upper layers of soil in forests are easily polluted by lead emissions25. It can be inferred from the last paragraph that scientists A) are puzzled by the mystery of forest pollutionB) feel relieved by the use of unleaded gasolineC) still consider lead pollution a problemD) lack sufficient means to bat lead pollutionPassage Four Questions 26 to 30 are based on the following passage. Exercise is one of the few factors with a positive role in longterm maintenance of body , that message has not gotten through to the average American, who would rather try switching to light beer and lowcalorie bread than increase physical exertion. The Centers for Disease Control, for example, found that fewer than onefourth of overweight adults who were trying to shed pounds said they were bining exercise with their diet. In rejecting exercise, some people may be discouraged too much by caloricexpenditure charts。s creativityC) lighten children39。s artistic interestsC) tapping children39。s chances of eventually being admitted to toprated schools and universities. Several more progressive programs have introduced free play as a way out for the heavyintellectualizing in some Japanese kindergartens.16. We learn from the first paragraph that many Americans believe A) Japanese parents are more involved in preschool education than American parentsB) Japan39。s because the prescription drugs available for the flu need to be taken soon after the illness sets in. As for colds, the sooner aperson starts taking overthecounter remedy, the sooner relief will e. The mon cold and the flu are both caused by viruses. More than 200 viruses can cause cold symptoms, while the flu is caused by three viruses flu A, B and C. There is no cure for eitherillness, but the flu can be prevented by the flu vaccine ( ~~ ), which is, for most people, the bestway to fight the flu, according to the ALA. But if the flu does strike, quick action can help. Although the flu and mon cold have manysimilarities, there are some obvious signs to look for. Cold symptoms such as stuffy nose, runny nose and scratchy throat typically develop gradually, and adults and teens often do not get a fever. On the other hand, fever is one of the characteristic features of the flu for all ages. And in general, flu symptoms including fever and chills, sorethroat and body aches e on suddenly and are more severe than cold symptoms. The ALA notes that it may be particularly difficult to tell when infants and preschool agechildren have the flu. It advises parents to call the doctor if their small children have flulikesymptoms. Both cold and flu symptoms can be eased with overthecounter medications as well. However,children and teens with a cold or flu should not take aspirin for pain relief because of the risk of Reye syndrome(綜合癥) ，a rare but serious condition of the liver and central nervous syndrome . There is, of course, no vaccine for the mon cold. But frequent hand washing and avoiding close contact with people who have colds can reduce the likelihood of