4. Is friction important to cars? Why? A. No, because friction has no effect on cars. B. No, because friction cannot slow down cars. C. Yes, because friction causes the cars to stop. D. Yes, because friction causes the cars to move. 5. Why do tires have hollows and bumps? A. in order to move fast B. in order to slide on the surfaces C. in order to drag over the surfaces D. in order to hold on to different surfaces​