虽然我们把生命三分之一的宝贵时间,花在睡眠方面,但是没有人晓得何以人类必须睡眠。这可能是人们的一种习惯,同时睡眠也能令脑部得休息的机会。究竟一个人每天的睡眠时间应该有多长?这是一个因人而异的问题,不过,睡眠时间虽 Although we spend a third of our precious time on sleep, no one knows why humanity has to sleep. This may be a habit of people, while sleep can make the brain have a chance to rest. How long should a person sleep every day? This is a problem that varies from person to person. However, although the time of sleep