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托福阅读词汇题：persistent

2015-08-26 15:34:22来源：网络

　　【托福阅读题型：persistent词汇题】托福阅读中词汇题是重要题型之一。根据托福阅读题型不同来进行专项练习，是短期提高托福阅读能力的有效方法。同学们需要多加练习哦!

　　查看全部：托福阅读题型分类练习之词汇题

　　托福阅读词汇题：persistent

　　【Paragraph 2】When crayfish are kept continuously in the dark, even for four to five months, their compound　eyes continue to adjust on a daily schedule for daytime and nighttime vision. Horseshoe crabs kept in the dark　continuously for a year were found to maintain a persistent rhythm of brain activity that similarly adapts their eyes on a　daily schedule for bright or for weak light. Like almost all daily cycles of animals deprived of environmental cues, those　measured for the horseshoe crabs in these conditions were not exactly 24 hours. Such a rhythm whose period is　approximately—but not exactly—a day is called circadian. For different individual horseshoe crabs, the circadian　period ranged from 22.2 to 25.5 hours. A particular animal typically maintains its own characteristic cycle duration with　great precision for many days. Indeed, stability of the biological clock's period is one of its major features, even　when the organism's environment is subjected to considerable changes in factors, such as temperature, that　would be expected to affect biological activity strongly. Further evidence for persistent internal rhythms appears　　when the usual external cycles are shifted—either experimentally or by rapid east-west travel over great distances.　Typically, the animal's daily internally generated cycle of activity continues without change. As a result, its activities are　　shifted relative to the external cycle of the new environment. The disorienting effects of this mismatch between　　external time cues and internal schedules may persist, like our jet lag, for several days or weeks until certain cues　such as the daylight/darkness cycle reset the organism's clock to synchronize with the daily rhythm of the new　environment.(Biological Clocks)

　　The word “persistent” in the passage is closest in meaning to

　　○adjusted

　　○strong

　　○enduring

　　○predicted

　　The word duration in the passage is closest in meaning to

　　○length

　　○feature

　　○process

　　○repetition

　　答案见下一页：

本文关键字: 托福阅读题型 托福阅读训练 词汇题

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