根据下列材料请回答 23～30 题：
Ways to Reduce Exposure to Air Pollution
1 A report published recently brings bad news about air pollution．It suggests that it could be as damaging to our health as exposure to the radiation from the 1 986 Ukraine nuclear power plant disaster．The report was published by the UK’S Royal Commission on Environmental Pollution．But what can city people do to reduce exposure to air pollution? Quite a lot，it turns out．
2 Avoid walking in busy streets．Choose side streets and parks instead．Pollution levels can fall a considerable amount just by moving a few meters away from the main pollution source—exhaust furies(废气)．Also don’t walk behind smokers．Walk on the windward(顶风的)side of the street where exposure of pollutants(污染物)can be 50 percent less than on the downwind(顺风的)side．
3 Sifting on the driver'S side of a bus can increase your exposure by 10 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．
第 23 题 Paragraph 2_________
A When you get up
B Where you stand while waiting to cross a road
C Where you walk
D Where you sit on a bus and how you travel
E When you go to bed
F When pollution levels rise and fall