The only horizontal forces on the car are the force of air resistance and the force of the road. Because the car travels at a constant velocity, the sum of these two forces must have a magnitude of

and it must point towards the center of the circle. If you add the forces

,

,

,

,

to the force

one at a time, it is clear that the only

could possibly point toward the center of the circle. Therefore, answer (C) is correct.