the answer is d. accelerate because an unbalanced force acting on an object causes it to accelerate because the force changes the object's velocity. Velocity is a vector quantity that describes both speed and direction. When a force acts on an object, it changes the object's velocity by changing its speed, its direction, or both. If the force is unbalanced, meaning it is stronger in one direction than in the opposite direction, then the object will accelerate in the direction of the stronger force. This acceleration means that the object's velocity is changing, either by speeding up, slowing down, or changing direction.