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  3. Could a plant virus have found a way to infect humans? It has always been assumed that plant viruses cannot infect animals, and

Could a plant virus have found a way to infect humans? It has always been assumed that plant viruses cannot infect animals, and

admin2015-07-31  60
问题     Could a plant virus have found a way to infect humans? It has always been assumed that plant viruses cannot infect animals, and vice versa, but plant viruses are known to be【C1】______in human faeces(粪便).
    Now Didier Raoult at the University of the Mediterranean in Marseille, France, and his team think a pepper virus is making people【C2】______, too. They have found RNA from the pepper mild mottle virus in the faeces of 7 percent of the 304 adults they tested. Those with the virus were more【C3】______to report fever, abdominal pain and itching(痒)than those without it, his team found.
    Not everyone is convinced, however. Because Raoult looked at many possible【C4】______, he would be expected to find a few that randomly【C5】______more common in virus-positive people, says Robert Garry, a virologist at Tulane University in New Orleans, Louisiana. Moreover, in order to enter a cell and replicate, a virus must bind to a receptor on its surface, and a plant virus would be highly unlikely to【C6】______a receptor on a human cell, says Garry.
    One possibility, Raoult says, is that the virus does not infect human cells【C7】______. Instead, the naked viral RNA may alter the【C8】______of the cells through a mechanism similar to RNA interference, in which the presence of certain RNA sequences can【C9】______genes on and off. Raoult’s team is now working to【C10】______more direct evidence that the virus does infect humans.
A)abundant F)function K)situations
B)appear G)gather L)surprisingly
C)available H)likely M)symptoms
D)capacity I)recognise N)tested
E)directly J)sick O)turn
【C5】
选项
答案B
解析 动词辨析题。空格在副词的后面，且本句中由that引导的定语从句缺少谓语，因此应填动词。根据句意可知，他能在一些病毒携带者身上找到一些随机______的较普遍的病症，结合选项来看，可以与“症状”搭配的只有appear“出现”，故为答案。
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