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       DNA（Deoxyribonucleic acid）is one of the most important discoveries in science. DNA is the plan for the human being ，as a blueprint is the plan for building. DNA makes a person look the way he does. A person’s DNA. comes from a mixing of his parents’ DNA . That’s why a child looks like his parents. But ，besides controlling things such as height and hair color，DNA can also give people diseases，Scientists are now studying DNA to cure diseases.

In the seventies, scientists developed a process called recombinant (重新组合) or RDNA. Although it sounds difficult to understand，RDNA simply means taking DNA from one animal or plant and putting it into another. By doing so ， scientists can create new beings. In so doing，scientists can better understand DNA，especially what parts of DNA do what parts of DNA do what. After they understand DNA，scientists can begin to cure diseases. Often，the new being created will itself be the cure.

Besides curing diseases，RDNA research can also do other things. For example，scientists in Japan have already created“super-trees”Trees help humans，because they take CO₂， which poisons humans ，from the air and turns it into oxygen， which lets humans breathe.“Super-trees” do this too，but do it much faster. As things such as cars and factories have already put much CO₂ in the area，“super-trees”are badly needed.

Unfortunately，there is serious danger in RDNA research.  Scientists want to create animals to cure old diseases，but these new animals may also create new diseases. It will be a serious problem if the animals escape from the science laboratory and into nature. As these animals are not natural，they may  let loose  many new powerful diseases.

      As a result，RDNA research will create many solutions （解决方案），but it will also create many problems.

1．From the passage，we can know that a boy looks like his parents because       

      A．he is son of his parents

      B．his parents’ DNA decides his appearance

      C．he has received DNA from his father or his mother

      D．scientists have put some of his parents’ DNA into him

2．What does the underlined expression “let loose”probably mean？

       A．let．．．go free      B．get rid of            C．absorb                D．survive

3．What is the best title for the passage？

       A．The DAN Research in Japan

       B．A New Way of DNA Research in Japan

    C．The Causes and Effects of DNA Research

       D．The Advantages And Disadvantages of RDNA

4．The following statements are true abort RDNA research EXCEPT      

       A．the research has been stopped because the created animals carry virus

       B．super-trees might be widely planted around the world

       C．scientists have not completely understood DNA

       D．RDNA research will benefit human beings a lot