题目内容：
阅读下文，回答题。More Than 8 Hours Sleep—Too Much of a Good Thing
1 Although the dangers of too little sleep are widely known, new research suggests that people who sleep too much may also suffer the consequences. Investigators at the University of (California, in San Diego found that people who clock up, 9 or 10 hours each weeknight appear to have more trouble falling and staying asleep, as well as a number of other sleep problems, than people who sleep 8 hours a night. People who slept only 7 hours each night also said they had more trouble falling asleep and feeling refreshed after a night's sleep than 8-hour sleepers.
2 These findings, which DL Daniel Kripke reported in the journal Psychosomatic Medicine, demonstrate that people who want to get a good night's rest may not need to set aside more than 8 hours a night. He added that "it might be a good idea” for people who sleep more than 8 hours each night to consider reducing the amount of time they spend in bed, but cautioned that more research, is needed to confirm this.
3 Previous studies have shown the potential dangers of chronic shortages of sleep. For instance, one report demonstrated that people who habitually sleep less than 7 hours each night have a higher risk of dying within a fixed period than people who sleep more.
4 For the current report, Kripke reviewed the responses of 1,004 adults to sleep questionnaires ,in which participants indicated how much they slept during the week and whether they experienced any sleep problems. Sleep problems included waking in the middle of the night, arising early in the morning and being unable to fall back to sleep, and having fatigue interfere with day-to-day functioning.
5 Kripke found that people who slept between 9 and 10 hours each night were more likely to report experiencing sleep problems than people who slept 8 hours. In an interview, Kripke noted that long sleepers may struggle to get rest at night simply because they spend too much time, in bed. As evidence, he added that one way to help insomnia is to spend less time in bed. “It stands to reason that if a person spends too long a time in bed，then they'll spend a higher percentage of time awake. “ he said.
Paragraph 1____ A．Kripke's Research Tool
B．Dangers of Habitual Shortages of Sleep
C．Criticism on Kripke's Report
D．A Way of Overcoming Insomnia
E．Sleep Problems of Long and Short Sleepers
F．Classification of Sleep Problems
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