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 1986 Ukraine nuclear power disaster.The report was published by the UK Royal Commission on Environmental Pollution.But what can city people do to reduce exposure to air pollution? Quite a lot, it turns out.

　　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 fumes(烟气).Also don’t walk behind smokers.Walk on the windward side of the street where exposure to pollutants can be 50 percent less than on the downwind side.

　　Sitting on the driver’s side of a bus can increase your exposure by 10 percent, compared with sit- ting on the side nearest the pavement.Sitting upstairs on a double-decker 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 than that at street level, because underground pollution is mostly made up of tiny iron particles thrown up by wheels hitting the rails.But diesel and petrol fumes have a mixture of pollutants.

　　When you are crossing a road, stand well back from the curb 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.

　　There are large sudden pollution increases during rush hours.Pollution levels fall during night-time.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.
If you take a bus in a big city in China, you should sit _____.

A.on the left side in the bus

B.on the right side in the bus

C.in the middle of the bus

D.at the back of the bus