Cats are creatures of habit．They like to go to sleep about the same time every day and for a certain length of time．They seem to have a natural clock inside them that tells them when to sleep．
Cats increase their regular sleep with occasional cat naps (打盹)．Some experts feel that humans could also benefit from this habit．Cat naps help to build up energy in the body．They are also a good way to get rid of trouble! Since cats have the same moods(情绪) as humans, some experts believe that people can improve their moods．People might become happier．
A number of famous people have copied cats by taking cat naps during the day．The naps would usually last from 15 to 30 minutes．
Winston Churchill took cat naps．So did Presidents Harry Truman, John F．Kennedy and Lyndon B．Johnson．These famous men were known for their energy．They were also able to work long hours, often into the night．Napping was their secret．
Perhaps more people learn from cats and take naps to feel better and live longer!
Naps usually last_______．
A.three hours
B.less than half an hour
C.forty-five minutes
D.fifty-five minutes