2017-07-26 14:35:14 来源：启达教育网
People often say that a dog is man's best friend. Over thousands of years, man has taught his dogs to do many kinds of work besides guarding the home. For example, sheepdogsare famous for their ability to control a flock of hundreds of sheep.
65体育投注 have beenused to aid disabled people for centuries. A guide dog can lead its blindowner. Nowadays, dogs can be taught to turn on light switches, openrefrigerator doors and dial the telephone for their disabled owners. For themajority of people, however, dogs are simply pets and friends for both youngand old members of the family.