If a piano player softly taps a key and then hits the same key with a lot of force,the second note will sound louder.What will differ between the sound waves of the two sounds

A)  timbre
B)  frequency 
C)  amplitude
D)  wavelength

Sound Waves

Vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.

Amplitude

The extent or range of a vibratory movement, measured from the position of equilibrium, commonly used to describe the magnitude of sound waves or other oscillations.

Frequency

The number of occurrences of a repeating event per unit of time, often used in the context of waves (such as sound or light) to indicate cycles per second (Hz).