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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

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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
【C7】
选项
答案E
解析 副词辨析题。空格在infect human cells的后面，且本句不缺少基本的句子成分，因此应填副词修饰动词infect。根据句意可知，植物病毒可能并不______感染人体细胞，这里是对上段中提出的质疑的辩驳，结合选项来看directly“直接地”符合句意，故为答案。
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