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欧洲人津津乐道这些老笑话的原因是：
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The word "customized"(Paragraph 5) can best be substituted by
作者笔下的“老妇人”最突出的特质是：
The word "depleted"(Paragraph 3) can be substituted by
Part A
Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D. (40 points)
Mark Twain once observed that giving up smoking is easy. He knew, because he'd done it hundreds of times himself. Giving up for ever is a trifle more difficult, apparently, and it is well known that it is much more difficult for some people than for others. Why is this so？
Few doctors believe any longer that it is simply a question of will power. And for those people that continue to view addicts as merely "weak", recent genetic research may force a rethink. A study conducted by Jacqueline Vink, of the Free University of Amsterdam, used a database called the Netherlands Twin Register to analyse the smoking habits of twins. Her results suggest that an individual's degree of nicotine dependence, and even the number of cigarettes he smokes per day, are strongly genetically influenced.
The Netherlands Twin Register is a voluntary database that is prized by geneticists because they allow the comparison of identical twins (who share all their genes) with fraternal twins (who share half). In this case, however, Dr. Vink did not make use of that fact. For her, the database was merely a convenient repository of information. Instead of comparing identical and fraternal twins, she concentrated on the adult fraternal twins, most of whom had completed questionnaires about their habits, including smoking, and 536 of whom had given DNA samples to the register.
The human genome is huge. It consists of billions of DNA "letters", some of which can be strung together to make sense (the genes), but many of which have either no function, or an unknown function. To follow what is going on, geneticists rely on markers they have identified within the genome. These are places where the genetic letters may vary between individuals. If a particular variant is routinely associated with a particular physical feature or a behaviour pattern, it suggests that a particular version of a nearby gene is influencing that feature or behaviour.
Dr. Vink hopes that finding genes responsible for nicotine dependence will make it possible to identify the causes of such dependence. That will help to classify smokers better (some are social smokers while others are physically addicted) and thus enable "quitting" programmes to be customised.
Results such as Dr. Vink's must be interpreted with care. Association studies, as such projects are known, have a disturbing habit of disappearing, as it were, in a puff of smoke when someone tries to replicate them. But if Dr. Vink really has exposed a genetic link with addiction, then Mark Twain's problem may eventually become a thing of the past.
The author cites the example of Mark Twain to show that
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