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Research into DNA has had a significant impact on medicine. Through recombinant DNA technology, scientists can modify microorganisms so that they become so-called factories that produce large quantities of medically useful drugs. This technology is used to produce insulin, which is a drug used by diabetics, and interferon, which is used by some cancer patients. Studies of human DNA are revealing genes that are associated with specific diseases, such as breast cancer. This information is helping physicians to diagnose various diseases, and it may lead to new treatments. For example, physicians are using a technology called chimeriplasty, which involves a synthetic molecule containing both DNA and RNA strands, in an effort to develop a treatment for a form of hemophilia.
Forensic science uses techniques developed in DNA research to identify individuals who have committed crimes. DNA from semen, skin, or blood t
A. DNA’ s functions
B. DNA’ s applications
C. DNA’ s research
D. DNA’ s techniques

[单项选择] Research on friendship has established a number of facts, some interesting, even useful. Did you know that the average student has 5～6 friends, or that a friend who was previously an enemy is liked more than one who has always been on the right side Would you believe that physically attractive individuals are preferred as friends to those less comely, and is it fair that physically attractive defendants are less likely to be found guilty in court Unfortunately, such titbits don’’t tell us much more about the nature or the purpose of friendship. In fact, studies of friendship seem to implicate more complex factors. For example, one function friendship seems to fulfill is that supports the image we have of ourselves, and confirms the value of the attitudes we hold. Certainly we appear to project ourselves onto our friends; several studies have shown that we judge them to be more like us than they (objectively) are. This suggests that we ought to choose friends who are similar t
A. every student has five or six friends
B. judges are always influenced by a pretty face
C. ugly people find it harder to make friends than beautiful people
D. we lend to grow fond of people if we dislike them at first sight