第二节 完型填空 阅读下面短文，从短文后所给各题的四个选项(A、B、C和D)中选出能填入相应空白处的最佳选项。 If your mother wants to tell you something, she uses【B1】. Birds cannot【B2】as we do. But some birds can make sounds to【B3】their young of danger. They have their own【B4】to make the young birds do【B5】 things. The jackdaw(寒鸦)is a kind of blackbird that【B6】 in Europe. Jackdaws live together【B7】 flocks(群). Young jackdaws do not know their【B8】 . When an older jackdaw 【B9】 a dog, it makes a 【B10】 rattling(咯咯响的) sound. The younger birds know this sound 'means an enemy is【B11】 . The sound warns them and【B12】 them to know their enemies. If a young jackdaw is in a【B13】 place, a jackdaw parent flies【B14】 him from behind. The parent bird flies low over the young birds back. The parents tail feathers move quickly from side【B15】 side. It is trying to say,'【B16】 me.' At the same time, the parent calls【B17】 ,'Key-aw, key-aw. 'The parents means, 'Fly【B18】 with me. 'The young bird then follows the older one home. Young jackdaws do not have to learn【B19】 certain sounds mean. They know the【B20】 of these sounds from the time they hatch. 【B1】