题干

下列有关遗传和进化的叙述中,正确的是(   )

A:某种群中若A的基因频率在一段时间后由0.4增加到0.6,a的基因频率由0.6下降到0.4,因为无新基因产生,可认为该种群没进化

B:培育三倍体无籽西瓜过程中,四倍体母本上所结的就是无籽西瓜

C:患病双亲生一个正常的女儿,则可推知该病为显性遗传病

D:DNA限制性内切酶是作用于磷酸与脱氧核糖之间的化学键以及氢键

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C

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    I don't think there is anything more important than health. “Health is the greatest wealth,” wise people say. You can't be good at your studies or work well when you are ill.

    If you have a headache, toothache, backache, earache or bad pain in the stomach, if you complain of a bad cough, if you run a high temperature and have a bad cold, or if you suffer from high or low blood pressure, I think you should go to the doctor. The doctor will examine your throat, feel your pulse, test your blood pressure, take your temperature, sound your heart and lungs, test your eyes, check your teeth or have your chest X-rayed. After that, he will advise some treatment, or some medicine. The only thing you have to do is to follow his advice.

    Speaking about doctor's advice, I can't help telling you a funny story. An old gentleman came to see the doctor. The man was very ill. He told the doctor about his weakness, memory loss and serious problems with his heart and lungs. The doctor examined him and said there was no medicine for his disease. He told his patient to go to a quiet place for a month and have a good rest. He also advised him to eat a lot of meat, drink two glasses of red wine every day and take long walks. In other words, the doctor advised him to follow the rule: "Eat with pleasure, drink with pleasure and enjoy life as it is." The doctor also said that if the man wanted to be well again, he shouldn't smoke more than one cigarette a day. A month later the gentleman came into the doctor's office. He looked cheerful and happy. He thanked the doctor and said that he had never felt a healthier man." But you know, doctor," he said, “it's not easy to begin smoking at my age.”