2. 外语
  3. Dogs were first domesticated from wolves at least 17,000 years ago, but perhaps as early as 150,000 years ago based upon recent

Dogs were first domesticated from wolves at least 17,000 years ago, but perhaps as early as 150,000 years ago based upon recent

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问题     Dogs were first domesticated from wolves at least 17,000 years ago, but perhaps as early as 150,000 years ago based upon recent genetic fossil and DNA evidence. In this time, the dog has developed into hundreds of breeds with a great degree of 【B1】______. For example, heights at the 【B2】______range from just a few inches to roughly three feet, and colors range from white to black, with reds, grays, and browns 【B3】______in tremendous patterns.
    Dogs are highly social animals and this similarity in their 【B4】______behavioral system accounts for their trainability, playfulness, and ability to fit into human 【B5】______and social situations. This has earned dogs a unique position in the 【B6】______of interspecies relationships. The loyalty and 【B7】______that dogs demonstrate as a part of their natural instincts are 【B8】______to be reflections of the human idea of love and friendship, leading many dog owners to view their pets as full-fledged family members. 【B9】______. Dogs play a variety of roles in society and are often trained as working dogs. 【B10】______. In many countries, the most common and perhaps most important role of dogs is as a companion. 【B11】______
【B1】
选项
答案variation
解析 由空前的of可推测，所填词应是名词。variation在此意为“差别，区别”。
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