摘 要: | Dogs are flesh-eating animals. From the Stone Age( 石器时代) menlived in caves( 洞穴). The dogs first became man?s friends. Soon the mentrained( 训练) the dogs to help people in the hunt to carry their burdens(担子), to guard their camps and so on.Dogs have a fine sense of smell ( 嗅觉). They can go in search ofmissing things. For example, a golden seal(图章) in a museum(博物馆)was missing some years ago, and the policemen searched for it every-where in vain(徒劳). Finally a dog found the go…
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