单选题Directions：In this part，you will have l5 minutes to go over the passage quickly and answer the questions on Answer Sheet l．For questions l-7，choose the best answer from the four choices markedA，B，C　and　D．For questions 8-10，complete the sentences With the information given in the passage．
Indoor Pollution
　　Since the early eighties we have been only too aware of devastating effects of large—scale environmental pollution．Such pollution is generally the result of poor government planning in many developing nations or the shortsighted，selfish policies of the already industrialized countries which encourage a minority of the world’s population to squander the majority of its natural resources．
　　While events such as the deforestation of the Amazon jungle or the nuclear disaster in Chernobyl continue to receive high media exposure，as do acts of environmental sabotage，it must be remembered that not all pollution is on this grand scale．A large proportion of the world’s pollution has its source much closer to home．The recent spillage of crude oil from an oil tanker accidentally discharging its cargo straight into Sydney Harbor not only caused serious damage to the harbor fore— shores but also created severely toxic fumes which hung over the suburbs for days and left the angry residents wondering how such a disaster could have been allowed to happen．
　　Avoiding pollution can be a fulltime job．Try not to inhale traffic fumes：keep away from chemical plants and building sites；wear a mask when cycling．It is enough to make you want to stay at home．But that，according to a growing body of scientific evidence，would also be a bad idea．Research shows that levels of pollutants such as hazardous gases。particulate matter and other chemical nasties are usually higher indoors than out，even in the most polluted cities．Since the average American spends l 8 hours indoors for every hour outside．it looks as though many environmentalists may be attacking the wrong target．
　　The latest study, conducted by two environmental engineers, Richard Corsi and Cynthia How- ard-Reed, of the University of Texas in Austin, and published in Environmental Science and Technology, suggests that it is the process of keeping clean that may be making indoor pollution worse. The researchers found that baths, showers, dishwashers and washing, machines can all be significant sources of indoor pollution, because they extract trace amounts of chemicals from the water that they use and transfer them to the air.
　　Nearly all public water supplies contain very low concentrations of toxic chemicals,' most of them left over from the otherwise beneficial process of chlorination. Dr. Corsi wondered whether they stay there when water is used, or whether they end up in the air that people breathe. The team conducted a series of experiments in which known quantities of five such chemicals were mixed with water and passed through a dishwasher, a washing machine, a s