[填空题]Cats are{{U}} (36) {{/U}}of habit~ They like to go to sleep about the same time every day and for a certain{{U}} (37) {{/U}}of time. They seem to have a{{U}} (38) {{/U}}clock inside them that tells them when to sleep. Cats{{U}} (39) {{/U}}their regular sleep with{{U}} (40) {{/U}}catnaps. Some experts feel that human could also benefit from this habit. Catnaps help to build up{{U}} (41) {{/U}}in the body. They are also a good way to overcome{{U}} (42) {{/U}} . Since cats have moods{{U}} (43) {{/U}}to those of humans, some experts believe that{{U}} (44) {{/U}} {{U}} (45) {{/U}}.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.{{U}} (46) {{/U}}. Perhaps more people could learn from eats and take naps to feel better and live longer!