The main idea is how force relates to changing motion. In everyday terms, pushing harder on an object usually changes its motion more than pushing softly, because the stronger push imparts a larger effect on how quickly or in what direction the object speeds up or slows down. This is the intuitive view students learn first: bigger force often means a bigger change in motion, especially when you’re comparing the same object under similar conditions. That’s why this statement fits best for practice at this level. Remember, mass does matter in real situations: heavier objects don’t accelerate as much with the same push as lighter ones, so the amount of change can vary with mass. But for the simple relationship the question aims to test, a stronger force generally leads to a greater change in motion. The other ideas don’t fit the basic idea as neatly: saying mass has no effect is not accurate because mass influences how much motion changes; a force can start motion from rest (so motion isn’t required to be already happening); and volume isn’t what determines how force changes motion.