题目内容
12．Cockroaches（蟑螂） are the most unpleasant of all insects．Seemingly large and fast，and they live in the most disgusting conditions．It's no wonder the first reaction of many to seeing a cockroach is to try to destroy it，and few would drop a tear at the thought of the entire species dying out．
But，of course，things are not so simple．Unpleasant though they are，according to biologists the ill-famed cockroach is essential to the survival of the planet's delicate ecosystem．
According to Srini Kambhampati，professor and chairman of the biology department at the University of Texas，the disappearance of cockroaches would play havoc with the nitrogen cycle．
As a leading expert on roaches，he said："Most cockroaches feed on rotten organic matter，which traps a lot of nitrogen．Cockroach feeding has the effect of releasing that nitrogen （in their waste）which then gets into the soil and is used by plants．In other words，extinction of cockroaches would have a big impact on forest health and therefore indirectly on all the species that live there．"
The professor also warned that the Earth's 5，000to 10，000cockroach species are also an important source of food for many birds and small mammals like mice and rats．
In turn，these killers themselves are food of many other species like cats，wolves and snakes，as well as eagles and other big birds．
Any cut to the number of cockroaches would thus have a harmful effect on the wellbeing of all these species that could have a destroying effect on wildlife across that world．
Of course，there's not much chance of a cockroach extinction level event happening any time soon．Still，although it was once believed that they would be one of the few creatures to survive even a nuclear Third World War，that idea has since been considered untrue．
28．What is the main idea of this passage？A
A．The hated cockroach is essential to the survival of the planet's delicate ecosystem．
B．The cockroach is a harmful species which is expected to die out in the near future．
C．Nobody will feel sad at the fact that the entire species of cockroach is dying out．
D．Let's destroy cockroaches without mercy because they polluted the environment．
29．From what Professor Kambhampati said in Paragraph 5，we can learn thatB．
A．cockroaches eat rotten organic matter to get nitrogen
B．nitrogen can make the soil suitable for plants to grow
C．cockroaches'dying out directly destroy all the species
D．plants benefit from cockroaches'getting into the soil
30．Which of the following belong to"these killers"in Paragraph 7？D
A．Cockroaches．
B．Mice and rats．
C．Cats and wolves．
D．Snakes and eagles．
31．We can infer from the last paragraphs thatA．
A．cockroaches can survive a nuclear war
B．cockroaches might cause a world war
C．cockroaches will never be extinct at all
D．cockroaches also need to be protected．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了讨厌的蟑螂对这个星球脆弱的生态系统的生存至关重要．
解答 28．A．主旨大意题．根据第三段Unpleasant though they are，according to biologists the ill-famed cockroach is essential to the survival of the planet's delicate ecosystem可知这篇文章的主要思想是讨厌的蟑螂对这个星球脆弱的生态系统的生存至关重要；故选A．
29．B．细节理解题．根据第五段Most cockroaches feed on rotten organic matter，which traps a lot of nitrogen．Cockroach feeding has the effect of releasing that nitrogen （in their waste）which then gets into the soil and is used by plants可知氮可以使土壤适合植物生长；故选B．
30．D．细节理解题．根据倒数第三段In turn，these killers themselves are food of many other species like cats，wolves and snakes，as well as eagles and other big birds可知蛇和鹰是蟑螂杀手；故选D．
31．A．推理判断题．根据最后一段Still，although it was once believed that they would be one of the few creatures to survive even a nuclear Third World War，that idea has since been considered untrue可知．cockroaches可以在核战争中生存下来；故选A．
点评 本文是一篇人物故事类阅读，题目涉及多道细节理解题，推理判断题，主旨大意题．做题时学生应仔细阅读原文，把握文章主要内容，联系文章上下文内容并结合所给选项含义，从中选出正确答案，一定要做到有理有据，切忌胡乱猜测．
