Answer:c. Frequency
Explanation:By definition frequency is the number of cycles per second, or the number of oscillations per second, measured in Hertz (Hz), then 1 Hz means one cycle or oscillation in one second, 10 Hz means 10 cycles in one second and so on. Also for motors specially is used rpm that stands for revolutions per minute. You could transform Hz into rpm if needed, but for waves, e.g., sound, electricity, etc. is used generally Hertz
