A cylinder is observed to be rolling freely at a constant speed on a horizontal surface. Which of the following statements is true? a.It is possible that the cylinder is both rolling and sliding at the same time, i.e. that v, the speed of the centerpoint, is not = to rw. b.If the cylinder is rolling without slipping, there must be a non-zero friction force exerted by the surface. c.It is not possible for the cylinder to roll unless friction is present. d.Even if the surface has friction, the cylinder cannot roll without slipping. e.If friction is present it is not possible for the motion to occur without loss of energy. Would the answer be b.? For rolling without slipping, static friction must be present. Thanks.