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MOCK TEST 5 Why does the author mention "unihemispheric slow-wave sleep (USWS)"?

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Sleep in Marine Mammals

Marine mammals, such as dolphins and whales, face unique challenges when it comes to sleeping. These animals must come to the surface to breathe air, yet they cannot afford to be completely unconscious while doing so. To address this, many marine mammals have developed unihemispheric slow-wave sleep USWS . In USWS, one hemisphere of the brain remains awake while the other enters a deep sleep. This adaptation allows the animal to continue swimming, surface for air, and stay alert to threats.

Studies have shown that dolphins use USWS to sleep while navigating and avoiding obstacles. Mother dolphins demonstrate another pattern called echelon swimming, where the calf rests in the mother's slipstream as she swims. This strategy enables the calf to rest without being stationary, highlighting the importance of movement even during rest periods.

Contrastingly, evidence suggests whales exhibit a different sleep strategy. Whales are observed floating near the surface in a motionless state, resembling a deep, meditative rest. This might indicate reliance on group vigilance, where the pod collectively watches for danger. These varied adaptations underscore the balance marine mammals must achieve between the necessity of sleep and the need for survival.

1.Why does the author mention "unihemispheric slow-wave sleep (USWS)"?

A. To suggest that marine mammals sleep less deeply than other animals

B. To explain how marine mammals can sleep without drowning

C. To compare sleep patterns in dolphins and whales

D. To illustrate the brain structure of marine mammals

你的答案：

正确答案：B

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题干翻译：作者为什么要提到“单半球慢波睡眠（USWS）”？定位信息：USWS 出现在第一段中部：To address this, many marine mammals have developed unihemispheric slow-wave sleep (USWS). In USWS, one hemisphere of the brain remains awake while the other enters a deep sleep. 前文关键信息：These animals must come to the surface to breathe air, yet they cannot afford to be completely unconscious… 逻辑关系：问题 → 解决方案选项分析：B. To explain how marine mammals can sleep without drowning 正好解释“怎么睡而不死” A. suggest sleep is less deep 文中说的是 deep sleep，不是“睡得浅” C. compare dolphins and whales对比是在后面段落，USWS 本身是机制解释，不是对比 D. illustrate brain structure没讲解剖结构，只讲功能

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