Chronic insomnia is a major public health problem. And too many people are using__1__ therapies，even while there are a few treatments that do work. Millions of Americans __2__awake at night counting sheep or have a stiff drink or __3__an pill，hoping it will make them sleepy.__4__ experts agree all that self-medicating is a bad idea，and the causes of chronic insomnia remain__5__.

　　Almost a third of adults have trouble sleeping，and about 10 percent have__6__ of daytime impairment that signal true insomnia. But __7__the complaints，scientists know surprisingly little about what causes chronic insomnia，its health consequences and how best to treat it，a panel of specialists __8__together by the National Institutes of Health concluded Wednesday. The panel called__9__a broad range of research into insomnia，__10__that if scientists understood its __11__causes，they could develop better treatments.

　　Most，but not all，insomnia is thought to __12__other health problems，from arthritis and depression to cardiovascular disease. The question often is whether the insomnia came first or was a result of the other diseases and how trouble sleeping in__13__complicates those other problems. Other diseases __14__，the risk of insomnia seems to increase with age and to be more __15__among women，especially after their 50s. Smoking，caffeine and numerous __16__drugs also affect sleep.

　　The NIH is spending about $200 million this year on sleep-related research，some__17__to specific disorders and others __18__the underlying scientific laws that control the nervous system of sleep. The agency was__19__the panel‘s review before deciding what additional work should be__20__ at insomnia.

　　1. [A] unproven [B] unknown [C] improper [D] imperative

　　2. [A] fall [B] lie [C] seem [D] become

　　3. [A] prescribe [B] pop [C] abuse [D] experiment

　　4. [A] And [B] Though [C] Thus [D] But

　　5. [A] peculiar [B] anonymous [C] mysterious [D] unexpected

　　6. [A] signals [B] symptoms [C] signs [D] symbols

　　7. [A] in addition to[B] except for [C] owing to [D] for all

　　8. [A] pulled [B] collected [C] brought [D] drawn

　　9. [A] on [B] for [C] up [D] in

　　10. [A] noting [B] notifying [C] nosing [D] nominating

　　11. [A] undertaking[B] underlining [C] underlying [D] undermining

　　12. [A] cause [B] accompany [C] follow [D] attend

　　13. [A] short [B] case [C] essence [D] turn

　　14. [A] inside [B] outside [C] aside [D] besides

　　15. [A] common [B] popular [C] frequent [D] regular

　　16. [A] conscription[B] description [C] subscription[D] prescription

　　17. [A] aimed [B] targeted [C] designated [D] designed

　　18. [A] examining [B] inspecting [C] verifying [D] assessing

　　19. [A] conducting [B] awaiting [C] receiving [D] considering

　　20. [A] assigned [B] charged [C] directed [D] attended