题目

For a bird, to fly hundreds or thousands of miles each spring and fall is a difficult and dangerous journey, one that not all birds can survive. 【1】 There is more than one single reason for different birds to migrate(迁徙), but it all comes down to survival.Birds are migrating for a meal.For all birds, one of the main driving forces behind migration is food. If all birds were to stay in the same places year-round, food there would become not enough. 【2】 But as the food supplies decrease in the fall, they return to the southern areas.【3】Over millions of years, birds have developed关于声现象，下列说法中正确的是（ ）A．“闻其声而知其人”主要是根据声音的响度来判断的B．“不敢高声语，恐惊天上人”中的“高”指声音的音调高C．中考期间学校周围路段禁鸣喇叭，这是在声音传播的过程中减弱噪声D．用超声波能粉碎人体内的“小石头”，说明声波具有能量