A wheel of radius R is rolling on a horizontal surface. Its center is moving forward with speed v. A point on the wheel a distance r/3 below the center is moving forward at a speed 2v/3. The wheel is A) rolling without slipping. B) not rotating at all. C) made of rubber. D) slipping because its angular speed is too low to be rolling without slipping. E) slipping because its angular speed is too high to be rolling without slipping.