阅读理解 Are you tired?Do you often catch colds and flu?If so, you might consider changing your sleep habits. Good health demands good sleep.Studies have shown that most people need eight hours of sleep each night.Americans, however, on average, get only seven hours.Onethird of us get just six hours, and good health is not simply a matter of how much sleep you get, but also the type of sleep you get. Nonrapid eye movement (NREM) sleep allows your body to grow and repair itself.During NREM sleep, your muscles relax.Your heart rate and breathing rate decrease.Your eyes roll slowly back and forths then they stop moving.Most of the sleeping you do is NREM sleep. Rapid eye movement (REM) sleep restores your brain.During REM sleep, you dream.You may not remember every dream, but every time you sleep, you dream.Your eye s move back and forth quickly. Your breathing rate and heartbeat increase.Your muscles become paralysed (麻痹的). About 25 percent of your sleep is REM sleep.You need enough of both kinds of sleep to be healthy. Is it a real concern if you don't get enough good sleep?It certainly is.Poor sleep puts you and others at risk. More than 100,000 car accidents are caused each year by drivers who nod off (打盹). Almost $100 billion is lost yearly in the business and environmental field.People deprived _ of sleep have been factors in the Challenger space tragedy, the Exxon Valdez oil spill (溢出), and the Chernobyl nuclear reactor accident.So do yourself and everyone around you a favour.Don't cheat yourself out of good sleep! 1. This passage is mainly about________. A. why people dream B. what happens during REM sleep C. why people catch colds and flu D. the importance of sleep 2. Most sleep at night is________. A. NREM sleep B. REM sleep C. good quality sleep D. sleep that makes you become paralysed 3. 'Good sleep' can be described as________. A. getting about eight hours of the two types of sleep B. sleeping soundly through the night C. getting more than seven hours of sleep each night D. having sleep that prevents accidents 4. To help the readers understand the effects of poor sleep habits, the writer________. A. explains the two types of sleep B. compares the two kinds of sleep C. mentions several disasters D. explains all the risks 5. The underlined phrase 'deprived of' in the last paragraph means '________'. A. not wanting B. stopped from having C. trying to get D. asking for