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  3. Despite the fact that today virus are known to cause cancer in animals and in plants, there exists a great reluctance to accept

Despite the fact that today virus are known to cause cancer in animals and in plants, there exists a great reluctance to accept

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问题     Despite the fact that today virus are known to cause cancer in animals and in plants, there exists a great reluctance to accept viruses as being of importance in human cancer. Basic biological phenomena generally do not differ strikingly as one goes from one species to another. It should be recognized that cancer is a biological problem and not a problem that is unique for man. Cancer originates when a normal cell suddenly becomes a cancer which multiplies widely and without apparent restraint. Cancer may originate in many different kinds of cell, but the cancer cell usually continues to carry certain traits of the cell of origin. The transformation of a normal cell into a cancer cell may have more than one kind of cause, but there is good reason to consider the relationships that exist between viruses and cancer.
    Since there is no evidence that human cancer, as generally experienced, is infectious, many persons believe that because viruses are infectious agents they cannot possibly be of importance in human cancer. However, viruses can mutate and examples are known in which a virus that never kills its host can mutate to form a new strain of virus that always kills its host. It does not seem unreasonable to assume that an innocuous latent virus might mutate to form a strain that causes cancer. Certainly the experimental evidence now available is consistent with the idea that viruses as we know them today could be the causative agents of most, if not all cancer, including cancer in man.
According to the passage, which is true?
选项 A、The transformation of a cell into a cancer has just one reason.
B、There is no relationship between viruses and cancers.
C、Viruses can mutate in some cases.
D、Viruses are not contagious.
答案C
解析 根据文章第二段第二句“viruses can mutate and examples are known in which a virus that never kills its host can mutate to form a new strain of virus that always kills its host．”可知，病毒是可以变异的，一个不能导致受体死亡的病毒会变异成一种新式病毒，这种病毒常常会导致受体的死亡。所以C正确。据此判断，本题选C。
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