职称英语理工类考试教材阅读理解重点文章以及译文(5)

　　Late-Night Drinking

　　Melatonin levels normally start to rise about two hours before bedtime. Levels then peak between 2 am and 4 am, before falling again3. Its the neurohormone that controls our sleep and tells our body when to sleep and when to wake, says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caffcinated coffee halves the bodys 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 decal. On average, subjects slept 336 minutes per night after drinking caffeinated coffee, compared with 415 minutes after decal. They also took half an hour to drop off4 - twice as long as usual - and jigged around5 in bed twice as much.

　　Because it can take many hours to eliminate caffeine from the body, Ohayon recommends that coffee lovers switch to decaf after lunch.

　　A melatonin levels need to be raised.

　　C coffee is a stimulant.

　　2. Which of the following tells us how caffeine affects sleep?

　　B Caffeine interrupts the flow of the hormone that prevents people from sleeping.

　　D Caffeine stays in the body for many hours.

　　A Different effects of caffeinated coffee and decaf on sleep.

　　C The fact that the subjects slept 415 minutes per night after drinking decaf.

　　4. What does the experiment mentioned in paragraph 4 prove?

　　B There are more melatonin concentrations in caffeine drinkers urine sample.

　　D Caffeine drinkers produce less sleep hormone.

　　A coffee lovers sleep less than those who do not drink coffee.

　　C people sleep more soundly at midnight than at 3 am.