de．
3 sifting on the driver’s side of a bus can increase your exposure by 1 0 percent，compared with sitting on the side realest the pavement．sifting upstairs on a double—decked(双层电车)can reduce exposure．it is difficult to say whether traveling on an underground train is better or worse than taking the bus．air pollution on underground trains tends to be less toxic(有毒的)than that at street level，because underground pollution is mostly made up of tiny iron particles(粒子)thrown up by wheels hitting the rails，while diesel(柴油机)and petrol fumes have a mixture of pollutants．
4 when you are crossing a road，stand well back from the curb(路缘)while you wait for the light to change。every meter really does count when you are close to traffic．as the traffic begins to move，fumes can be reduced in just a few seconds。so holding your breath for just a moment can make a difference，even though it might sound silly．
5 there are large sudden pollution increases during rush hours．pollution levels fall during nighttime．the time of year also makes a big difference．pollution levels tend to be at their lowest during spring and autumn when winds are freshest．extreme cold or hot weather has a trapping effect and tends to cause a build—up of pollutants．
23 paragraph 2_________
24 paragraphs 3_________
25 paragraph 4_________
26 paragraph 5________
a when you get up
b where you stand while waiting to cross a road
c where you walk来源：
d where you sit on a bus and how you travel
e when you go to bed
f when pollution levels rise and fall
27 air pollution can be as harmful to one's health___________
28 traveling on an underground train can reduce exposure___________
29 pollution levels are lower__________
30 it's wise to stay away from heavy traffic____________
a on the downwind side
b during rush hours
c in spring and autumn
d to toxic air来源：
e between autumn and winter
f as exposure to nuclear radiation
第4部分：阅读理解(第31—45题，每题3分，共45分)
下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。
第一篇stop eating too much
clean your plate! ”and“ be a member of the clean—plate club! "just about every kid in the us has heard this from a parent or grandparent．often，it's accompanied by an appeal：“just think about those starving orphans(孤儿)in africa!”sure，we should be grateful for every bite of food．unfortunately, many people in the us take too many bites． instead of staying“clean the plate”，perhaps we should save some food for tomorrow．
according to news reports，us restaurants are partly to blame for the growing bellies (肚子)．a waiter puts a plate of food in front of each customer, with two to four times the amount recommended by the government；according to a usa today story．americans traditionally associate quantity with value and most restaurants tyro give them that． they prefer to have customers complain a
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