考研综合演练与答案详解（1）
Passage 1
Environment pollution is a worldwide concern. Some scientists believe that there are four major pollutions surrounding us——water pollution, atmosphere pollution, noise pollution and electromagnetic pollution. And some even think electricity can cause cancer. Can electricity really cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. 1) __________________________________________________. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro -wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate, or the worst kind of paranoia.
2) __________________________________________________. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence “suggests a casual link” between extremely low-frequency electromagnetic fields (ELF) ——those having very long wave lengths——and leukemia, lymphoma and brain cancer. While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60 hertz magnetic field as “a possible, but not proven, cause of cancer in humans.”
3)____________________________________________________.
At the heart of the debate is a simple and well-understood physical phenomenon: when an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. 4) __________________________________________________. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth's own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter, this is far less than the electric fields that the cells themselves generate.
How could such minuscule forces pose a health danger? The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X- rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such “ionizing” radiations have been clearly linked to increased cancer risks and there are regulations to control emissions.
5) __________________________________________________. Though there is a body of laboratory work showing that exposure to ELF field can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found.
[A] Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency ( EPA ).
[B] But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies.
[C] However, there are still some people insist that even low-frequency electromagnetic fields is extremely harmful to human's health.
[D] But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect.
[E] The report is no reason to panic - or even to lest sleep, ff there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the Whit House. But now no one can deny that the issue must be taken seriously and that much more research is needed.
[F] Consequently, the epidemiological studies, taken as a whole, consist of a few early low-quality studies, some of which yielded positive effects, and later, higher-quality studies, which yielded negative studies. If power lines really caused cancer, it is natural to expect the later studies to confirm the earlier studies. Instead, this has all the earmarks of a nonexistent effect.
[G] For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak.
【文章大意及结构分析】
这是一篇关于电磁波是否致癌的科普文章。电能导致癌症吗?在一个依靠电力运行的社会里，这个观点似乎荒唐。可是越来越多的科学家和新闻工作者指出，接触电磁场有增加白血病和其他恶性疾病危险的可能性。但这种可能性还没有定论。美国环境保护署发布报告指出，甚低频的电磁场和白血病，淋巴瘤和脑癌之间有“—种偶然的联系”。我们没有理由为此恐慌，即使有患癌症的危险，这种风险也是很小的。尚且对它的证据还有很大的争议。争议的焦点是一个简单的物理现象：当电流通过电线时，会产生一个对周围物体施加压力的电磁场。这个压力极其微弱。比细胞自身产生的电场压力还低得多。如此小的力量不会对健康构成威胁。最近，科学家研究强大辐射离子。离子化的辐射毫无疑问会增加患癌症的风险。可是，通过流行病学研究，也不能证明它们之间的因果关系。
本文共分6个自然段。作者采用“提出问题——分析原因——解决问题”这一行文格式。第一段作者提出问题：电流能导致癌症吗? 第二段到第五段中对这一问题进行分析。第二段说环境保护机构报告：电磁场和某些癌症之间有“偶然的联系”；第三段讲，对这一结论的证据争论很大。第四段讲，电磁场的压力很小，对人体无害；第五段又提出，离子化辐射增加患癌症的风险。第六段是结论，根据所做的流行病学研究，没有发现它们之间的因果关系，而且试验室对动物的实验，也没有发现电流致癌的生理机制。
【解题思路与答案详解】
1) 【答案】[B]。本题在第一段的中间。根据它的上下文来推断它的内容。它前面讲，电流能导致癌症吗?在一个基本上依靠电力来运行的社会里，这个观点似乎有点荒唐（Can electricity really cause cancer? In a society that literally runs on electric power, the very idea seems preposterous.）。它后面讲，这种可能性还没有定论（The implications are unsettling）。其中The implications就是解题的线索，本题的内容应该讲“这种可能性”。据此，我们可以确定选项[B]是正确答案。其意为：十几年来，越来越多的科学家和新闻工作者指出，接触电磁场有增加患白血病和其他恶性疾病风险的可能性。
2) 【答案】[A]。本题在第二段的开始。前一段讲到，越来越多的科学家和新闻工作者认为接触电磁场有增加患白血病和其他恶性疾病的风险，但没有得到证实。本段其余部分主要讲，美国环境保护署发出了最为严肃的政府警告。甚低频的电磁场和白血病，淋巴瘤和脑癌之间有“—种偶然的联系” （the EPA has put forward what amounts to the most serious government warning, …“suggests a casual link” between extremely low-frequency electromagnetic fields (ELF)…and leukemia, lymphoma and brain cancer）。据此推断，本题应该是一个过渡句或过渡句组，起承上启下的作用，连接这两个段落。另外其中the EPA也是一个解题的线索。所以选项[A]是正确答案。句意为：现在，“杞人忧天者”已经获得了来自美国环境保护署的正式的支持。
3) 【答案】[E]。 本题是一个独立的自然段，即文章的第三段。独立的段落有两种可能，一是过渡段，一是扩展段；这要根据它的前后段落的内容来判断。它前一段主要讲，EPA报告电流有某种致癌的危险；它后一段讲，争议的焦点是一个简单的，很好理解的物理现象（At the heart of the debate is a simple and well-understood physical phenomenon）等。据此可以推断，本段讲到关于这一问题的争论。所以，选项[E]是正确答案。这是一个典型的过渡段落。其意为：报告说没有理由恐慌——甚至失眠。即使有患癌症的危险，这种风险也是很小的。证据的争议性仍然很大，草案激起了布什政府内部很多争论。环境保护署是克服了五角大楼和白宫的强烈反对而发布此报告的。不过现在没有人否认有必要进行更多的研究并认真对待这个问题。
4) 【答案】[G] 。本题在第四段的中间。可以根据它的上下文来选择答案。它前面讲的是，争论的焦点是个简单的物理现象——当电流通过电线时，会产生一个对周围物体施加压力的电磁场（…when an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surr