A simple siren can be constructed by attaching a perforated disk to a motor and by spinning it while air flows through the perforation. As the disk spins, it starts and stops the flow of air, creating a series of pressure variations (sound). How fast would you need to spin the disk in revolutions per minute (RPM) for the frequency of these pressure variations to be 120Hz? Group of answer choices A. 432000 RPM B. 7200 RPM C. 120 RPM D. 60 RPM E. 2 RPM