[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 (41) ________ from this habit. Catnaps help to build up (42) ________ in the body. They are also a good way to overcome (43) ________. Since cats have moods similar to those of humans, some experts believe that (44)________________. (45) ________________. The naps would usually last from fifteen to thirty minutes. 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!