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【单选题】
上课时老师将一蜂鸣器固定在教鞭一端后迅速水平旋转，蜂鸣器音调竟忽高忽低变化，下列判断正确的是()。
A.
旋转时蜂鸣器发出的频率变化了
B.
由于旋转，改变了同学们听到的声音频率
C.
蜂鸣器音调变高时，一定是向远离观察者的方向运动
D.
音调的忽高忽低是由于波的干涉造成的
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
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B.
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