Which of the following statements is true of vibrations?
Question 3 options:

A)

Ultrasonic vibrations have a frequency lower than the range for normal hearing.

B)

The frequency of infrasonic vibrations is much too high to be heard by humans.

C)

Infrasonic vibrations are used in sonar equipment and to detect flaws in steel castings.

D)

Neither ultrasonic nor infrasonic vibrations can be heard by humans.