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标题: prep6一道逻辑题 [打印本页]

作者: 且敛风翼 时间: 2018-11-25 14:05
标题: prep6一道逻辑题

Lyme disease is caused by a bacterium transmitted to people by deer ticks. Deer ticks are almost never born infected with the bacterium, but they can pick it up from feeding on an infected host in any of the tick's three successive stages of development: larva, nymph, adult. Once infected, a tick remains infected through any subsequent developmental stages, but since a tick feeds on only one host in each stage, it follows that __________.

people can be infected only by being bitten by a tick that is either in the larval stage or in the nymph stage
people cannot be infected by a tick that picked up the Lyme disease bacterium in the adult stage
it is not possible for a person to be infected by a tick that is in the nymph stage or by a tick that was infected with the bacterium while in the nymph stage
people infected with the Lyme disease bacterium cannot transmit the bacterium to adult deer ticks
only deer ticks that are adults can transmit the Lyme disease bacterium to people

b说不会被成虫感染，c说不会被幼虫感染，但怎么判断什么时候寄生到人身上？？

作者: spicytaco 时间: 2018-11-25 14:36
Once infected, a tick remains infected through any subsequent developmental stages, but since a tick feeds on only one host in each stage

three successive stages of development: larva, nymph, adult

红色部分告诉你：如果tick已经在adult阶段了，人是安全的...因为tick不会换载体了；如果在larva或 nymph阶段，感染的tick都可以把人作为subsequent stage host ,而使人感染

所以B正确

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