题目

阅读理解Babies sleep about eighteen hours a day．Mrs. Thatcher and Napoleon both said they only needed to do it three or four hours a night．No one can live without sleep．But how much do we really need? Research（研究）by the National Sleep Foundation in Washington says that we all need eight hours’ sleep every night．Scientists have found that people who sleep for less than six and a half hours a night are more often ill than people who sleep for eight hours．Going without sleep also increases（增加）the chance of serious illness．“Workaholics（工作狂）”who sleep19．下列岩石中常含有化石和具有层理特点的是（　　）A．花岗岩B．玄武岩C．石灰岩D．大理岩