题目

关于声现象，下列说法中正确的是 A . 声音在各种介质中的传播速度一样大 B . “闻其声而知其人”主要是根据声音的响度来判断的 C . 用超声波可击碎人体内“结石”，说明声波能传递能量 D . 市区内“禁鸣喇叭”，采用的是在声音传播过程中减弱噪声 答案：CThough my grandfather is in his eighties, he is still as _________ as a young man and hates sitting around doing nothing all day.A．enthusiastic B．talkative C．energeticD．sensitive