Question

what happens to an object when unbalanced forces act on it?
it remains at rest.
it accelerates.
it loses mass
it moves at constant speed.

Explanation:

According to Newton's second - law of motion, when unbalanced forces act on an object, there is a net force. A net force causes an acceleration. An object at rest will start moving, and a moving object will change its speed or direction. Losing mass is not related to unbalanced forces acting on an object in the context of this basic force - motion relationship, and moving at a constant speed occurs when forces are balanced.

Answer:

It accelerates.