Answer:
C. Beats
Explanation:
When waves are interfering with each other, the sound is louder in some places and softer in others. As a result, we hear pulses or beats in the sound.
The answer is Carbonic acid
Gravity acts to accelerate the ball downward, and air resistance acts in a way to slow the ball along it's instantaneous velocity (no matter which way it's moving air applies a force in the opposite direction)
