单选题 {{B}}第三篇{{/B}}

{{B}} Late-night Drinking{{/B}}
Coffee lovers beware. Having a quick "pick-me-up" cup of coffee late in the day will play havoc with you sleep. As well as being a stimulant, caffeine interrupts the flow of melatonin, the brain hormone that send people into a sleep.
Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 a.m. and 4 a.m., before falling again. "It's the neurohormone that controls our sleep and tells our body when to sleep and when to wake," says Manrice Ohayon of the Stanford Sleep Epidemiklogy Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body's levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slept less well after a cup of caffeinated coffee than after drinking the same amount of decaf. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, compared with 415 minutes after decaf. They also took half an hour to drop off--twice as long as usual-- and jigged around in twice as much.
In the second phase of the experiment, the researchers woke the volunteers every three hours and asked them to give a urine sample. Shilo measured concentrations of a breakers were half those in decaf drinkers. The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers. In a paper accepted for publication in Sleep Medicine, the researchers suggest that caffeine blocks production of the enzyme the drives melatonin production.
Because it can take many hours to eliminate caffeine from the body, Ohayon recommends that coffee lovers switch to decal after lunch.

单选题 The author mentions "pick-me-up" to indicate that______.

【正确答案】 C

【答案解析】[解析] 利用题干中的核心结构(也是特殊结构)“pick-me-up”作为答案线索，找到答案相关句：Coffee lovers beware(谨慎)．Having a quick“nick-me-up”cup of coffee late in the day will play havoc with you sleep.(暗示咖啡影响睡眠)As well as being a stimulant(刺激物)，(该划线句说“咖啡因作为一种刺激物……”，因此可以得出结论“咖啡是一种刺激物”，C是答案)caffeine interrupts the flow of melatonin(褪黑激素)，the brain hormone that send people into a sleep．

单选题 Which of the following tells us how caffeine affects sleep?

单选题 What does paragraph 3 mainly discuss?

【正确答案】 A

【答案解析】[解析] 该题考察判断指定段落的大意，因此关注段落中的观点句。段落第一句中就出现了明显表示其所在的句子是观点的结构：“某某专家find(发现)……”Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six volunteers slent less well after a cup of caffeinated coffee than after drinking the saine amount of decaf．因此可以直接借助该句句意判断答案。该句说“Lotan Shilo和一个研究小组发现六个志愿者在喝了一杯含咖啡因的咖啡后其睡眠状况不如喝了等量的脱咖啡因的咖啡后睡眠好。”因此判断A“含咖啡因的咖啡和不含咖啡因的咖啡对睡眠带来的不同影响”是答案。

单选题 What does the experiment mentioned in paragraph 4 prove?

【正确答案】 D

【答案解析】[解析] 注意到备选项都是涉及到细节内容，因此在指定段落中一一进行查找和确认。同时注意每个备选项中的核心词/短语。The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers．(该句句意表明B的说法错误)In a paper accepted for publication in Sleep Medicine，the researchers suggest that caffeine blocks production of the enzyme that drives melatonin production． (该句句意表明A和C的说法错误)

单选题 The author of this passage probably agrees that______.

【正确答案】 B

【答案解析】[解析] 该题涉及到文章主题，首先把四个备选项一一进行分析比较，然后首先把剩下的文章最后内容看完：Because it can take many hours to eliminate caffeine from the body，Ohayon recommends that coffee lovers swish to decaf after lunch．从该句中可以推出B的内容正确。