Cats are animals of habit. They like to go to sleep 1._____
about same time every day and for a certain length of time. They 2._____
seem to have natural clock inside them that tells them 3._____
when sleeping. Besides their regular sleep, cats take naps(打盹). 4._____
Some scientists think that people should also take cat nap. The 5._____
habit would do good for people's health. 6._____
Cat naps helped build up energy in the body. 7._____
Since cats have moods(情绪) like these of people, 8._____
scientists believe that people can improve their moods with 9._____
cat-napping. People might become more happier and more active.10.____