A. the object’s motion does not change. b. the inertia of the object increases. c. the weight of the object decreases. d. the object accelerates.

D. the object accelerates

Explanation:
Based on Newton's first law: "An object will maintain its state of rest or motion unless an external force acts on it"
An unbalanced forced means that there is a net force acting on the object. This will lead the object to either speed up, slow down, come to rest or change its direction.
This means that the net force caused by the unbalanced force will lead the object to accelerate.

Hope this helps :)