If the forces acting on an object are balanced, wihat must be true about the motion of this object?

The correct answer to the question is : D) Be moving at a constant velocity.

EXPLANATION:

As per Newton's first laws of motion, every body 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 changes the state of rest or motion of a body. Balanced force is responsible for keeping the body to be either in static equilibrium or in dynamic equilibrium.

As per the options given in the question, the last one is true for an object under balanced forces.

this could be newton#'s law of cooling. the cooling curve is exponential