Sleep experts say it is likely that people make more mistakes at work than at other times. They say people should not carry out important duties when they feel 11 And they say the best thing to do is to take a nap. About twenty minutes of rest is 12 you need. Experts say this provides extra energy and can increase your effectiveness 13 the end of the day. But experts warn that a nap 14 last no more than twenty to thirty minutes. A longer nap will put the body into deep sleep and waking up will be 15 .
练习：
1. A sweet B sound C bad D enough
2. A checking B sharing C continuing D meeting
3. A lovely B likely C fondly D finely
4. A for B at C in D with
5. A at least B at most C at last D at first
6. A ability B health C thinking D life
7. A experiment B reform C idea D way
8. A repeat B improve C change D leave
9. A work B mistakes C energy D time
10. A never B seldom C too D also
11. A ready B good C sleepy D awake
12. A all B few C any D nothing
13. A unless B while C until D during
14. A would B may C might D should
15. A helpful B difficult C easy D happy
白天打个盹
医学专家称大多数美国人睡眠不足。他们说更多的美国人需要在一天中间做短暂休息。他们建议人们在继续其他活动之前小睡一会。
今年早期的一个研究发现，白天睡几分钟的那些人死于心脏病的可能性较小。该研究六年期间，跟踪2300名希腊成年人。研究显示：成年人白天打盹半小时，一周三次，其心脏病致死的概率比不打盹的人要低37%。研究组织者称最有力的证据来自于工作岗位上的人群。他们说打盹可以减轻工作压力，从而改善健康。
一些欧洲和拉美的行业多年来一直支持白天打一会盹的观点。他们敦促人们放下工作回家去打个盹后再回来工作。在美国，有些公司让员工在办公室稍作休息。他们认为这不仅会减少失误和事故，还会增加工作量。
睡眠专家认为人们很可能工作时比其他时候犯错更多。他们认为人们不该在感到困倦的时候承担重要任务。此时最该做的是打个盹。你只需要休息20分钟。专家称这会给你的一天带来额外的能量和效率。但专家也提到，打盹不要超过20至30分钟。打盹时间稍长就会使身体陷入深层睡眠，很难醒来。
答案：DCBAA DBCDB DCACDB
第三篇 Cell Phone Lets Your Secret Out (A)
Your cell phone holds secrets about you. Besides the names and 1 that you've programmed into it, traces of your DNA linger on the device, according to a new study.
DNA is genetic material that 2 in every cell. Like your fingerprint, your DNA is unique to you-- 3 you have an identical twin. Scientists today routinely analyze DNA in blood, saliva, or hair left 4 at the scene of a crime. The results often help detectives identify 5 and their victims. Your cell phone can reveal more about you 6 you might think.
Meghan J. McFadden, a scientist at McMaster University in Hamilton, Ontario, heard about a crime in which the suspect bled onto a cell phone and later dropped the 7 This made her wonder whether traces of DNA lingered on cell phones--even when no blood was involved. 8 she and colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volunteers. They used swabs to collect 9 traces of the users from two parts of the phone: the outside, where the user holds it, and the 10 , which is placed at the user's ear.
The scientists scrubbed the phones using a solution made mostly 11 alcohol. The aim of washing was to remove all detectable traces of DNA. The owners got ,Heir phones 12 for another week. Then the researchers collected the phones and repeated the swabbing of each phone once more.