The correct answer to this question is D) Unbalanced forces.
EXPLANATION:
From Newton's first laws of motion, we know that everybody continues to be at state of rest or of uniform motion in a straight line unless and until, it is compelled by some external unbalanced forces acting on it.
Hence, it is the unbalanced force which is responsible for creating the motion in a body, changing the direction of motion or speed of the body.
No balanced force can change the state of the body. The body will be either in dynamic equilibrium or in static equilibrium due to the balanced forces.
Hence, the correct option of this question is unbalanced forces.
