If an object is having a constant positive acceleration, what can we assume about the forces on it?

If an object has a net force acting on it, it will accelerate. The object will speed up, slow down or change direction. ... If however, the forces are balanced (in equilibrium) and there is no net force, the object will not accelerate and the velocity will remain constant.

c is the correct answer hope this !

a=c and then d= c because of the band so you get ac/dc and you add them together you get sound waves