Answer: B
Step-by-step explanation:
Newton's first law it's law of inertia.
An object at rest will remain at rest (or an object in motion in a straight line at a constant velocity will remain that way) unless it is acted by an unbalanced force.
In A for the ball to slow down and stop, an external force (like friction with air or the floor) needs to be taken in consideration.
In B we can see how we need to make a force on the wagon to make it move.
In C we have an other Newton 's law, force equals mass times acceleration (2nd law)
In D we can see how it does not move because the forces on the box are balanced.