Explanation:
Acceleration is defined as the change in velocity over time.
When there is an increment or increase in the magnitude of velocity of a moving body then it is known as positive acceleration.
Whereas when there is a decrease in magnitude of velocity of a moving body then it is known as negative acceleration.
Thus, we can conclude that positive acceleration occurs when an object speeds up.
It is an example of reflection of wave. C.
The one that both benefits each other is the one I think it's mutalistic