2017届高考英语一轮复习专题强化训练：专题2 阅读理解第1讲专题强化训练（含解析）_高考复习指南

2017届高考英语一轮复习专题强化训练：专题2 阅读理解第1讲专题强化训练（含解析）

　　(2016·河南洛阳统一考试)It is 7 am and the

　　Why is it that teens find it difficult to get themselves out of bed in time every morning or stay sharp and focused during the first couple of hours of school?

　　During adolescence，the body goes through many changes and these include a shift in sleep patterns.Researchers from MIT have been tracking the body’s need for sleep in teenagers.They found that though adolescents need as much as 9.5 hours of sleep a day，they get to bed later and later with each passing year.In fact，the sleep cycle shifts later by as much as 12 to 18 minutes each year between the ages of 10 and 20 ! So by the time a 10－year－old who sleeps at 8 pm grows to be 17 or 18：30 pm or 11 pm.(褪黑激素) that is secreted (分泌) by the pineal gland—a tiny structure deep inside the brain.Melatonin regulates the body’s natural day－night rhythms.It causes a person to become sleepy by lowering his body’s core temperature.In teensout the night.This makes it difficult for teens to fall asleep earlier as they did in their younger years.Likewise，the effect of melatonin continues until much later in the morning，making it hard for them to wake up early.

　　A study found that at least one in four teens is tired and falls asleep in school at least once a week.During sleep，important body functions and brain activities happen.So how can teenagers get their sleep enough? The American Academy of Pediatrics (AAP) recommends that middle and high schools should start later—not before 8：30 am.This should give teens some more time to sleep at night.【解题导语】　本文是一篇说明文。早睡才能早起晚睡会导致早上赖床睡觉周期的改变实际上受制于大脑中一种被称为褪黑激素的荷尔蒙。xt day you should ________．解析：选C。细节理解题。文章第一段提到为什么孩子们早上不愿起床第二段紧接着分析原因说明孩子们睡觉晚是他们早上赖床的原因即C项正确。h 3 refer to?