Municipal sewage is of relatively¹ recent origin as a pollutant². It was first brought to

　　public attention in the 19th century by a London physician who showed that the city's cholera³ outbreak had been caused by just one contaminated well. Even though the contamination of  drinking water by disease germs has been nearly eliminated in this country, hundreds of  communities are still discharging raw sewage into streams and rivers.?When we consider that this sewage contains effluents from toilets, hospitals, laundries,industrial plants, etc., then the potential of the pollutants⁴ as a health hazard is apparent.?

　　The problem of municipal sewage disposal is complicated by the fact that, years ago, mostcities combined their storm and waste disposal sewers⁵. Many of these combined systems work well, but others cannot cope with sudden heavy rains. When such storms occur, water mixed with sewage may flood and disable treatment plants unless bypassed, untreated, into a stream. In either case, the people may have little protection for several days from these wastes that may contain disease germs.?Even if adequately treated to eliminate the health hazard, sewage is aesthetically⁶

　　undesirable⁷ because of odors and colors produced. Detergents⁸ have posed a particular disposal problem. Although there is no indication that they are injurious to health, they can cause foaming⁹, which can clog¹⁰ treatment plants and, at the least, spoil the scenic¹¹ beauty of streams.?Rural and suburban¹² residents should be aware that septic tanks and cesspools are a potential source of pollution to ground water supplies. This is especially true in the

　　suburban areas with a high population density¹³ and with no municipal sewage disposal and treatment system available. In some areas, sewage disposal is accomplished¹⁴ by cesspools. Soil research is furnishing guidelines for more effective and safer use of systems such as these.?

　　1. This passage is concerned primarily with the _____ .

　　A. problems of waste disposal?

　　B. dangers of drinking from wells?

　　C. turbidity¹⁵ of polluted water?

　　D. outbreak of cholera

　　答案为

　　2. The author mentions the London cholera epidemic¹⁶ to _____ .?

　　A. prove that the city refused to deal with pollution?

　　B. prove that medical science once knew little about pollution?

　　C. introduce the idea of contaminated water supplies?

　　D. recall a historical fact?

　　答案为

　　3. In densely¹⁷ populated suburban areas, a danger exits from _____ .?

　　A. streams that do not flow directly to open bodies of water?

　　B. cesspools and septic tanks that contaminate water supplies?

　　C. storm and waste disposal sewers that have been combined?

　　D. the undesirable odors of sewage?

　　答案为

　　4. In developing the main point, the author makes use of _____ .

　　A. scientific arguments?

　　B. convincing testimony¹⁸?

　　C. common sense observations?

　　D. analogy?

　　答案为

　　答案：

　　1A

　　此题为主旨题。线索词为"sewage"、"pollutant"、"sewage disposal"等，这些词贯穿文章始终，可见A项符合题意。B、C、D三项皆为文中细节，不能反映主题。?

　　2C

　　此题为细节题。答案在第一段。线索词为"London cholera"。此题考查作者

　　引用的目的。A项与文中所述事实相反。B项文中未涉及此话题。D项"London cholera"是一个"historical fact"，却不是作者引用之目的。?

　　3B

　　此题为细节题。答案在最后一段的主题句中。线索词为"suburban"、"source of pollution"和"ground water"。?

　　4C

　　此题为篇章结构题。作者首先提出排污系统为污染源，然后通过观察、分析、归纳来阐述观点，而没用A项"科学论证"、B项"令人信服的证据"或D项"类比"。

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