Achickenlaysanegg.Youfeelsleepy.Andatreelosesitsleaves....
问题详情：Achickenlaysanegg.Youfeelsleepy.Andatreelosesitsleaves.Allofthesethings,andmanymore,happeninacertainway,atacertaintimeeachdayoreachyear.Theytakeplacebecauseofsomethingcalledaninternalclock.The...