Despite the fact that today viruses
(病毒) are known to cause cancer in animals and in certain 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 cell 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 (特性) of the cell of origin. The
transformation of a normal cell into a cancer cell may have more than one kind
of cause, but them is good reason to consider the relationships that exist
between viruses and A. viruses are known to cause cancer in animals B. at present, human cancer is not believed to be contagious (传染的) C. there are many known causes for the transformation of a normal cell to a cancer cell D. results of experiments on plants and animals do not vary greatly from species tn species [单项选择]
Passage Three [单项选择]Passage 4
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 age
A. Viruses are known to cause cancer in animals and in plants. B. Many people don’t believe that viruses cause human cancer. C. Bioloigical phenomena don’t change much in animals and plants. D. Cancer may originate in certain kinds of cells. 我来回答: 提交
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