The answer is: C) waves.
A vibrating object (in this example drum) will produce sound waves in the air.
When the head of a drum is hit with a mallet, the drumhead vibrates and produces sound waves.
Sound that is perceptible by humans has frequencies from about 20 Hz to 20000 Hz.
Sound waves travel faster in more dense material, and the more dense the material the louder the sound is.
