Final answer:
The force required by Mr. Robbins to move the stroller is mainly determined by the stroller's mass, as per Newton's second law of motion, where force depends on mass and acceleration.
Step-by-step explanation:
The amount of force Mr. Robbins must use to push the stroller is most likely dependent on the stroller's mass. According to Newton's second law of motion, force is equal to mass times acceleration (F = ma). Thus, assuming other factors like friction and the slope of the surface are constant, a stroller with more mass will need more force to move it from rest or to accelerate it. This fact is illustrated in many dynamic situations, such as a child in a roller coaster car, where the force felt by the child depends on the mass of the child and the acceleration of the car.
When pulling a wagon or applying a force to any object, the increase in speed (velocity change) is a result of the force applied, which is directly related to the acceleration imparted on the object, which again brings us back to Newton's second law. The direction or velocity at which Mr. Robbins pushes the stroller doesn't demand more force unless he intends to change the speed (accelerate) the stroller; similarly, the distance over which he pushes doesn't inherently require more force, unless he is overcoming friction over that distance. Regarding option C, while the force required to maintain a certain velocity (constant speed) might be related to overcoming friction, it does not directly depend on the velocity itself.