填空题

Cats are (36)______of habit. They like to go to sleep about the same time every day and for a certain (37)______of time. They seem to have a (38)______clock inside them that tells them when to sleep. Cats (39)______their regular sleep with (40)______catnaps. Some experts feel that human could also benefit from this habit. Catnaps help to build up (41)______in the body. They are also a good way to overcome (42)______. Since cats have moods (43)______to those of humans, some experts believe that (44)________________________________. (45)________________________________. The naps would usually last from fifteen to thirty munutes. Winston Churchill took catnaps. So did Presidents Harry Truman, John F. Kennedy, and Lyndon B. Johnson. (46)________________________________. Perhaps more people could learn from cats and take naps to feel better and live longer!