Scientists have found that there are three 13 stages in a mosquitos assault. Stage one is at fifty feet away, when the insect first smells a man or a animal to 14 . Stage two is thought to come into operation about twenty-five feet from the target, when the insect becomes guided by the carbon dioxide breathed out by the intended victim. Stage three is when the mosquito is only a matter of inches from its 15 the warmth and moisture given off by the victim is the final clue.
The researchers then 16 how repellents interfere with its three-stage attack. They found repellents act more subtly than by just giving off a nasty smell. A Canadian researcher says that repellents appear to 17 mosquitoes first when it is following the carbon dioxide and second during the final approach, where the warmth and moisture are the insects 18 .
Air pervaded by one of the many chemical repellents stops the mosquito reacting to the victims carbon dioxide, and the repellent seems to affect the tiny hairs with which the insect senses moisture in the air. The sensors are blocked so that the 19 does not know whether it is flying through a moist current, or
the sensors are made to send the 20 signals.
A. examined B. animal C. wrong D. insect
E. bite F. Unfortunately G. inventing H. distinct
I. prey J. guide K. checked L. definite
M. Unnecessarily N. confuse O. discovering
11. O 12. F 13. H 14. E 15. I 16. A 17. N 18. J 19. D 20. C
少儿英语情景对话:市场
少儿英语情景对话:任何事
少儿英语情景对话:你现在忙吗?
少儿英语情景对话:太糟糕了
少儿英语情景对话:我们还是没动
少儿英语情景对话:该上学了
少儿英语情景对话:那是我吃午饭的时候
少儿英语情景对话:她现在在做什么?
少儿英语情景对话:X先生在吗?
少儿英语情景对话:我可以试穿一下吗?
少儿英语情景对话:我想要那个洋娃娃
少儿英语情景对话:我很赶时间
少儿英语情景对话
少儿英语情景对话练习:在首尔,就当自己是首尔市民
少儿英语情景对话:你妈妈是做什么的
少儿英语情景对话练习:找你的电话
少儿英语情景对话:采摘蒲公英
少儿英语情景对话练习
少儿英语情景对话:邀请
少儿英语情景对话汇总
少儿英语情景对话:我喜欢葡萄
少儿英语情景对话练习:我们去滑旱冰
少儿英语情景对话:你为什么不租一辆车?
少儿英语情景对话:看这个
少儿英语情景对话:我喜欢学校
少儿英语情景对话:Zoo 动物园
少儿英语情景对话:我不能告诉你
少儿英语情景对话:就餐用语
少儿英语情景对话练习:不要错过了
少儿英语情景对话:等不及吃了
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