8．Do you often feel tired in the morning even though you've been in bed for seven or eight hours the night before？Like many people，you are not sleeping as much as you think you are．In other words，your sleep efficiency is not that good．
Sleep experts define"sleep efficiency"as the percentage of time lying down that you are actually sleeping．According to journalism website Vox．com，the science of sleep efficiency is still young．There is no specific number for efficiency that's been proven as linked to poor health．However，according to a New York Times report about sleep quality，some experts estimate a rough range of 85percent or above as a reasonable place to be．Therefore，some tips for improving sleep efficiency are as follows：
Keep a consistent（一致的） sleep schedule
Go to bed and wake up at the same time，or relatively the same time，every day．Consistency is key to a good night's sleep，especially when it comes to waking up．When you have a consistent wake-up time，your brain adapts to this and moves through the sleep cycle in preparation for you to feel rested and alert at your wakeup time．
Avoid blue light at night
Blue light given off by the screens of computers，iPads and smartphones makes you feel more alert．Blue light tells your brain it's daytime．Experts suggest turning off your computers and smartphones 1hour or at least 30minutes before bed．
Take naps
If you aren't getting enough sleep at night，you're likely going to feel a strong desire to sleep in the afternoon．When this happens，you're better off taking a short nap than turning to caffeine or strong tea to keep you awake．A short nap will give you the rest you need to get through the rest of the afternoon，and you'll sleep much better in the evening．
21．According to the passage，we can learn that sleep efficiencyD．
A．is an advanced way to measure sleep quality
B．has close relationship with the state of health
C．is decided by the time you are lying in bed
D．can be greatly improved with certain measures taken
22．Which of the following may contribute to a better sleep in the evening？B
A．Taking a long afternoon nap．B．Sleeping for a while in the daytime．
C．Having a fixed go-to-bed time．D．Avoiding blue light in the evening．
23．What can we infer from the passage？D
A．Enough sleep will lead to a changeable wake-up time．
B．Blue light will affect the sleep due to its harm to the brains．
C．Waking up two hours before the body clocks means good sleep efficiency．
D.90% for sleep efficiency can possibly mean a quite good sleep state．
24．What will be the best title of the passage？B
A．Schedule your bedtime．B．Sleep well to be well．
C．Ensure long sleeping hours．D．Know more about your sleep．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了提高睡眠效率的几个方法：保持一致的睡眠时间表，夜间避免蓝光，白天适当小睡．
解答 21．D．细节理解题．根据文章第二段"Therefore，some tips for improving sleep efficiency are as follows"可知睡眠效率有一定的措施可以大大提高；故选D．
22．B．细节理解题．根据文章最后一段"A short nap will give you the rest you need to get through the rest of the afternoon，and you'll sleep much better in the evening"可知下午的休息，你会在晚上更好的睡眠；故选B
23．D．细节理解题．根据文章第二段"according to a New York Times report about sleep quality，some experts estimate a rough range of 85percent or above as a reasonable place to be"可知百分之85以上的睡眠效率就拥有相当好的睡眠质量；故选D．
24．B．主旨大意题．通读全文，可知文章主要描述了提高睡眠效率的几个方法，因此最佳标题为如何让自己睡得好；故选B．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
