You are out for a bicycle ride on a calm, windless day. you are heading northward on a level road and are experiencing a pressure drag force that pushes you toward the south. this air resistance explains why you have to keep pedaling to maintain your constant speed. if someone were to examine the air that you have left behind you after you have passed through it, they would find that the air's average velocity is(a) zero and that it is calm.(b) northward.(c) zero but that it is swirling rapidly in all directions.(d) southward.