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题目材料：
The cigarettes available in some countries increase a smoker's risk of contracting lung cancer more than the cigarettes available in others. In Akraland, long-term heavy smokers are three times as likely to contract lung cancer as nonsmokers, but in Brenovia they are eight times as likely to do so. Since long-term heavy smokers smoke approximately the same number of cigarettes in the two countries, cigarettes in Brenovia must be more dangerous than those in Akraland.
Which of the following, if true, most seriously weakens the argument?
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ALong-term heavy smokers form a substantially larger proportion of the population in Brenovia then in Akraland.
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BThe population of Akraland is on the whole older than the population of Brenovia, and lung cancer generally does not develop until after about twenty years of smoking.
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CIn both countries. smokers who give up smoking are less likely to develop lung cancer than are those who do not.
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DIn Akraland, fewer young people are taking up smoking now than was the case a few years ago.
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EAmong nonsmokers, lung cancer is less common in Brenovia than it is in Akraland, where people are often exposed to cancer-causing fumes from coal fires.
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