题目

完形填空 People have been raising pigeons (鸽子) for about 10,000 years. And pigeon keepers use different kinds of pigeons for different1. Some people use pigeons for2. For example, in parts of the world, people cook a special meal with pigeon to celebrate the New Year. Some people also3pigeons because they look especially 4. There are many interesting kinds of “pretty” pigeons. Different kinds of pigeons have interesting features (特点)5 long, soft tails or designs on their heads. The6of these kinds of pigeons enter them in7and the best looking pigeons are chosen to win prizes. Bu“ ”和“ ”A2和B2 ， 它们在一定条件下能发生化学反应，其反应微观示意图如图： （1）参加反应A2与生成物个数比为 ．（2）反应后物质是（填“混合物”、“化合物”）．（3）生成物化学式为（A、B表示）．