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  3. Discovered in the early 1800s and named ’ nicotianine’ , the oily essence now called nicotine is the main active ingredient of t

Discovered in the early 1800s and named ’ nicotianine’ , the oily essence now called nicotine is the main active ingredient of t

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问题     Discovered in the early 1800s and named ’ nicotianine’ , the oily essence now called nicotine is the main active ingredient of tobacco. Nicotine, however, is only a small component of cigarette smoke, which contains more than 4, 700 chemical compounds, including 43 cancer causing substances. In recent times, scientific research has been providing evidence that years of cigarette smoking vastly increases the risk of developing fatal medical conditions.
    In addition to being responsible for more than 85 per cent of lung cancers, smoking is associated with cancers of, amongst others, the mouth, stomach and kidneys, and is thought to cause about 14 per cent of leukemia and cervical cancers. In 1990, smoking caused more than 84,000 deaths, mainly resulting from such problems as pneumonia, bronchitis and influenza. Smoking, it is believed, is responsible for 30 per cent of all deaths from cancer and clearly represents the most important preventable cause of cancer in countries like the United States today.
    Passive smoking, the breathing in of the side-stream smoke from the burning of tobacco between puffs or of the smoke exhaled by a smoker, also causes a serious health risk. A report published in 1992 by the US Environmental Protection Agency(EPA)emphasized the health dangers, especially from side-stream smoke. This type of smoke contains more, smaller particles and is therefore more likely to be deposited deep in the lungs. On the basis of this report, the EPA has classified environmental tobacco smoke in the highest risk category for causing cancer.
    As an illustration of the health risks, in the case of a married couple where one partner is a smoker and one a nonsmoker, the latter is believed to have a 30 per cent higher risk of death from heart disease because of passive smoking. The risk of lung cancer also increases over the years of exposure and the figure jumps to 80 per cent if the spouse has been smoking four packs a day for 20 years. It has been calculated that 17 per cent of cases of lung cancer can be attributed to high levels of exposure to secondhand tobacco smoke during childhood and adolescence.
According to information in the text, intake of nicotine encourages
选项 A、blood circulation through the body
B、activity of other toxins in the blood.
C、formation of blood clots.
D、an increase of platelets in the blood.
答案B
解析 推理题。根据nicotine定位到第一段第二句，说到尼古丁只是4700多种化学混合物质之一，会导致很多种疾病，四个选项中只有B(增加血液中其他有毒物质的活动)是最能导致疾病的情况。
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