Questions 16 to 18 are based on the passage you have just heard.
A.Four to six hours.
B.Six to nine hours.
C.Around eight hours.
D.More than eight hours.
A.They may not be able to focus well.
B.They may get the feeling of being drunk.
C.They may lose much weight in a short period.
D.They may suffer from high blood pressure.
A.Training can make people sleep less temporarily.
B.Military people are used to being deprived of sleep.
C.People can bank sleep by sleeping more beforehand.
D.Sleeping earlier than usual makes people sleep less.
We waste a third of our lives sleeping. When there doesn't seem to be enough hours in the day, you yearn to be like the former British Prime Minister Margaret Thatcher, who was said to get by on just four hours' sleep a night. There is a quite a range in the number of hours we like to sleep. 80% of us manage between six and nine hours a night; the other 20% sleep more or less than this.
There is plenty of evidence that a lack of sleep has an adverse effect. We do not simply adjust to it—in the short-term it reduces our concentration, and if it's extreme it makes us confused and distressed, and turns us into such poor drivers of being drunk. The long-term effects are even more worrying. Repeatedly getting less sleep than you need over the course of decades is associated with an increased risk of obesity, diabetes, high blood pressure and heart diseases.
But while it might not be possible to train yourself to sleep less, researchers working with the military have found that you can bank sleep beforehand if you plan well in advance. At the Walter Reed Army Institute of Research they had people go to bed a couple of hours earlier than usual every night for a week. When they were subsequently deprived of sleep they didn't suffer as much as the people who hadn't had the chance to bank sleep in advance.
16. How much time do most people usually sleep every night?
17. What could happen if people didn't get enough sleep for a long time?
18. What do the researchers find about the military?
【小题17】该题对长时间缺乏睡眠的弊端提问。短文提到Repeatedly getting less sleep... is associatedwith an increased risk of obesity, diabetes, high blood pressure and heart diseases，即“长时间睡眠缺乏会提高人们患肥胖、糖尿病、高血压和心脏病的风险”，因此答案为选项D。
【小题18】此题是针对研究人员的研究发现提问。短文中提到But..., researchers working with themilitary have found that you can bank sleep beforehand if you plan well in advance. 由此可知，如果提前计划好，人们是可以将睡眠时间预存下来的，因此答案为选项C。