A、Most are insomniacs. B、Most are teenagers. C、Most are easily cured. D、Most suffer from hypersomnia. D这道题紧承上一道题，说话者指出，大多数病人受嗜睡症

You might think that most of the patients at sleep clinic are being treated for sleeplessness, commonly referred to as insomnia, but that is not the case. The majority of sleep-clinic patients suffer from disorders of excessive sleep—or hypersomnia. While most insomniacs somehow manage to drag themselves through the day and function at acceptable, although not optimal levels, this is not so for people who suffer from hypersomnia.
    They are incapacitated by irresistible urges to sleep during the day, often in inappropriate situations—at business meetings, in supermarkets, or at parties. Even more dangerous is their failure to remain awake when driving or operating machinery. Falling asleep in such situations could obviously be life-threatening.
    Many hypersomniacs suffer from narcolepsy, for which the primary symptom is excessive daytime sleepiness. Though not apparent in childhood, this symptom most often appears for the first time during the teen years and continues throughout a person’s life. The sleep attacks may occur as many as fifteen to twenty times during the course of the day and last for periods from fifteen minutes up to two hours.
    What can be done to help those suffering from narcolepsy? There are certain drugs that can help, and specialists suggest voluntary napping to decrease the frequency of such sleep attacks.
9. What is "hypersomnia"?
10. What does the speaker say about sleep-clinic patients?
11. When does narcolepsy usually first become apparent?
12. What can a narcoleptic do to prevent sleep attacks?