一般人们把声音频率超过()的声波称为超声波Ultrasound refers to sound waves with a frequency exceeding()

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一般人们把声音频率超过()的声波称为超声波Ultrasound refers to sound waves with a frequency exceeding()

A.10kHz

B.20kHz

C.10MHz

D.20MHz

E.20Hz

F.2000Hz

参考答案:

答案:20kHz