A、Longer duration of sleep. B、High efficiency of sleep. C、Better patterns of sleep. D、More security in sleep. B新闻最后提到，人类祖先从睡到树上转

(5)Humans need less sleep than other mammals, yet their slumber is more efficient, said researchers at Duke University in North Carolina. In their study, the scientists researched sleep patterns of hundreds of animals. They discovered humans sleep for shorter periods of time compared to other animals. The study also concluded that a human’s sleep is higher quality.(6)A deeper stage of sleep, called rapid eye movement sleep, or REM, makes up 25 percent of human’s sleep. In primates like lemurs or monkeys, REM sleep does not reach the five percent mark.
    "Humans are unique in having shorter, higher quality sleep," said David Samson, a study co-author. Samson’s research team found that humans can prosper with an average of seven hours of sleep a day. Other primates need as many as 14 to 17 hours of sleep. Samson said human sleep habits evolved during prehistoric times. Human ancestors moved from sleeping in trees to sleeping on the ground.(7)Better sleeping habits resulted in better sleep in a shorter amount of time.
5. What can we learn about human’s sleep?
6. What can we learn about REM?
7. What do the better sleeping habits result in?