Sleep is part of a person's daily activity cycle. There are several different stages of sleep, and they too occur in cycles. If you are an average sleeper,　your sleep cycle is as follows. When you first drift off into slumber (安睡), your eyes will roll about a bit, your temperature will drop slightly, your muscles will relax, and your breathing were slow and become quite regular. Your brain waves slow down a bit too, with the alpha rhythm of rather fast waves predominating for the first few minutes. This is called stage 1 sleep. For　the next half hour or so, as you relax more and more, you will drift down through stage 2 and stage 3 sleep. The lower your stage of sleep, the slower　your brain waves will be. Then about 40 to 60 minutes after you lose consciousness you will have reached the deepest sleep of all. Your brain waves will show the large slow waves that are known as the delta rhythm. This is stage 4 sleep.

　　You do not remain at this deep fourth stage all night long, but instead about 80 minutes after you fall into slumber, your brain activity level will increase again slightly. The delta rhythm will disappear, to be replaced by the　activity pattern of brain waves. Your eyes will begin to dart around under your closed eyelids (眼皮) as if you were looking at something occurring in　front of you. This period of rapid eye movement lasts for some 8 to 15 minutes　and is called REM sleep. It is during REM sleep period, your body will soon relax again, your breathing will grow slow and regular once more, and you will slip gently back from stage 1 to stage 4 sleep — only to rise once again to the surface of near consciousness some 80 minutes later.

　　1.The stages of sleep take on ____.

　　A) an irregular aspect. B) a regular aspect C) a punctual aspect D) a similar aspect

　　2.Stage 4 sleep lasts ____.

　　A) about 80 minutes

　　B) about 40 60 minutes

　　C) about 30 munutes

　　D) about 20 40 minutes

　　3.The brain waves are the slowest during ____.

　　A) stage 1 C) stage 4 B) stage 2 and stage 3 D) REM sleep

　　4.In the second paragraph the word “dart” means ____.

　　A) glare B) move rapidly or suddenly C) stop moving D) gaze

　　5.One of the features of REM sleep is that ____.

　　A) there are large slow waves, though rapid for the first few minutes

　　B) you have the deepest sleep

　　C) there are no brain waves

　　D) the brain waves are a little fast and the brain becomes a little active

　　参考答案：

　　1.答案B。文章的第二句告诉我们睡眠的不同阶段是周期性发生的，故睡眠的各阶段呈现规则的一面。

　　2.答案D。根据文章可知一个睡眠周期大约是 80分钟，而stage 4 sleep是睡眠的最后阶段，它发生在入睡后大约40至60分钟时，据此可推出stage 4 sleep持续20至40分钟。

　　3.答案C。文章第一段倒数第四句说“睡得越深，脑电波就越慢”，而 stage 4 sleep 是睡得最深的，故脑电波也是最慢的。

　　4.答案B。dart的后文说“眼睛好像看着发生在眼前的事”，又说“这种快速移动眼睛的阶段叫 REM sleep”，据此可知dart意为move quickly or suddenly(飞快地移动)。glare怒目而视;gaze凝视。

　　5.答案D。从第二段第一、二句可知大脑运动水平会再度略有提高，而 delta波消失， 取代的是脑电波运动图形。据此可知脑电波变得快了一点，大脑活跃些。而大的缓波和睡得 最深是 stage 4 sleep的特征，rapid for the first few minutes是stage 1 sleep的特征，整个睡眠阶段都是有脑电波的，故A，B和C皆错。