中考英语阅读理解(三)　介绍说明.docx

阅读理解(三)　介绍说明 A　[2018·朝阳一模] In the days before electricity, people dont worry much about sleep.They usually went to bed a couple of hours after sunset(日落) and woke at sunrise. After all, there wasnt much to do in those days after the sun went down.But then came the electric light bulb(电灯泡).And now we have satellite television, the Internet, 24-hour convenience stores, and longer hours at work.How much can we sleep? How much should we sleep? Like it or not, many of us are sleeping less on average(平均).In 1910, most Americans slept 9 hours a night.That dropped to 7.5 hours by 1975.In 2002, a study by the National Sleep Foundation found that the average American got only 6.9 hours.The news is even worse for people who work the night shift.They sleep an average of just 5 hours. Are we sleeping enough? Not if you believe in the old rule of eight hours of rest, eight hours of work, and eight hours of play.On the other hand, Norman Stanley, a British scientist who studies sleep, believes peoples sleep needs are different.Some people need as many as 11 hours, but others need as few as three.How much do you really need?“To find out,” he says,“simply sleep until you wake naturally, without the help of an alarm clock.Thats your sleep need.” Meanwhile, other scientists and researchers are searching for new ways to keep us awake longer.Some are developing chemicals(化学药品) that are safer and more powerful than caffeine, the chemical found in coffee and tea.One experimental drug, CX717, kept laboratory monkeys working happily for 36 hours.Further developments may allow people to safely stay awake for several days straight.One group of researchers is studying a gene(基因) found in some fruit flies that lets them get by on one-third the usual amount of sleep.Another group is even working on an electric switch that immediately wakes up a sleeping brain. The meanings of this research are huge.On the one hand, this could lead to a world where we work longer and longer hours with less a