(A) frequency in the audible range (X)
(B) frequency is greater than 20 kHz ()
(C) frequency lower than 20 Hz (X)
(D) all of above (X)
Answers: Ultrasonic have frequency is greater than 20 kHz.
(A) frequency in the audible range (X)
(B) frequency is greater than 20 kHz ()
(C) frequency lower than 20 Hz (X)
(D) all of above (X)
Answers: Ultrasonic have frequency is greater than 20 kHz.
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