The answer is D - the centripetal force is directed towards the center of the circular path. That is because the acceleration vector for centripetal motion always points radially inwards. Furthermore, this can be intuitive when looking at the direction of motion for the circular path. The velocity vector traces out the circular path, meaning that the velocity vector is always tangent to the circle. In circular motion, the velocity vector and acceleration vector are perpendicular; so, if the velocity vector is tangent to the motion, the acceleration vector (and thus centripetal force) must be perpendicular to that tangent line and will always point radially inwards/towards the center of the circular path.
