求教大全-B-2. 实在不能理解答案！！！ps：之前木有解答过

灭绝湿太

大全-B-2.    In the years since the city of London imposed strict air-pollution regulations on local industry, the number of bird species seen in and around London has increased dramatically. Similar air-pollution rules should be imposed in other major cities.
Each of the following is an assumption made in the argument above EXCEPT:
(A) In most major cities, air-pollution problems are caused almost entirely by local industry.
(B) Air-pollution regulations on industry have a significant impact on the quality of the air.
(C) The air-pollution problems of other major cities are basically similar to those once suffered by London.
(D) An increase in the number of bird species in and around a city is desirable.
(E) The increased sightings of bird species in and around London reflect an actual increase in the number of species in the area.
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答案选a。。。。。但是a明显就是assumption啊！~我选的是d。。。。

求解答！

chenjiao0121

你这样理解嘛，如果城市的空气不好主要是由两个原因引起的，比如汽车和local industry。各占50%。那随意控制一个也能有效果。所以A取非，原结论还是成立三。
相反，D取非的话，就不行了。原文说regulation推出more birds，根据逆否关系，no more birds 推出no regulation

灭绝湿太

你这样理解嘛，如果城市的空气不好主要是由两个原因引起的，比如汽车和local industry。各占50%。那随意控制一个也能有效果。所以A取非，原结论还是成立三。
相反，D取非的话，就不行了。原文说regulation推出more birds，根据逆否关系，no more birds 推出no regulation

-- by 会员 chenjiao0121 (2011/7/11 16:29:10)

 A里面有一句话“are caused almost entirely by” 表明了城市空气不好的最主要原因是local industry.....如果A取非，那么就是说local industry

只是次要原因，或者不相关，那么strict air-pollution regulations on local industry和空气的改善应该没有关系，或关系很不明显。A取非就是否定

了结论。

但是D只是表命明鸟数的增加是件好事儿，取非的话就是“鸟数的增加不是好事儿”，这个和空气改善没有直接关系吧。。。。取非对结论也没影响。

ps：鸟数增加有可能影响生态平衡，但不影响表示空气质量的好转......

这样来看，A还是不对阿！！！