理工類：補全短文練習題The Dangers
Most people know that cigarette smoking is harmful to their health.Scientific research shows that it causes many kinds of diseases.In fact，many people who smoke get lung cancel However， Edward Gilson has lung cancer， and he has never smoked cigarettes.He lives with his wife，Evelyn，who has smoked about a pack of cigarettes a day throughout their marriage. __________.(46)
No one knows for sure why Mr. Gilson has lung cancer.Nevertheless，doctors believe that secondhand smoke may cause lung cancer in people who do not smoke because nonsmokers often breathe in the smoke. from other people’s cigarettes.__________ (47)The US Environmental Protection Agency reports that about 53，000 people die in the United States each year as a result of exposure to secondhand smoke.
The smoke that comes from a lit cigarette contains many different poisonous chemicals.In the past.scientists did not也ink that these chemicals could harm a nonsmoker’s health. __________ (48)They discovered that even nonsmokers had unhealthy amounts of these toxic(有毒的)chemicals in their bodies.As a matter of fact，almost all of US breathe tobacco smoke at times，whether we realize it or not.For example，we cannot avoid secondhand smoke in restaurants，hotels and other public places.Even though many public places have nonsmoking areas，smoke flows in from the areas where smoking is permitted.It iS even harder for children to avoid secondhand smoke.__________ (49)Research shows that children who are exposed to secondhand smoke are sick more often than children who live in homes where no one smokes and that the children of smokers are more than twice as likely to develop lung cancer when they are adults as are children of nonsmokers.The risk is even higher for children who live in homes where both parents smoke
People are becoming very aware of the dangers of secondhand smoke. __________ (50)
A Recently，though，scientists changed their opinion after they studied a large group of nonsmokers.
B The Gilsons have been married for 35 years.
C 111is smoke is called secondhand smoke.
D However， secondhand smoke is dangerous to all people，old or young.
E As a result，they have passed laws which prohibit people from smoking in many public places. .
F In the United States，nine million children under the age of five live in homes with at least one smoker.
答案解析：
46 B 前一句主要講的是，Gilson與妻子Evelyn生活在一起，而Evelyn自打他們結婚以來一直是差不多每天一包煙。接下來顯然應選表示他們結婚年限的句子。
47 C 前～旬提到，不吸煙者時常吸入他人香煙中冒出的煙，接下來應首選對此煙加以定義的句子。
48 A 前一句講的是科學家們過去對二手煙的看法，接下來應選表示他們改變觀點的句子，因為下一句表明他們所持的觀點已與過去截然不同。
49 F 前一句提到了兒童與二手煙的問題。接下來的句子自然仍然與兒童有關。
50 E 前一句講的是人們逐漸意識到二手煙的危害性，因此接下來應首選表示人們采取措施，禁止公共場所吸煙的句子。