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: