颤动回声(fiutter echo)
参考答案:
同一声源原始脉冲声引起的一连串紧跟着的反射脉冲声。
____________, they have been struggling against the snowstorm for ten hours.
A.Up to now
B.By the time
C.From then on
D.In the future
甲因涉嫌盗窃被A县公安局取保候审,现甲的联系方式发生变动,甲应当在24小时以内向A县公安局报告。