The correct answer is the frictional force.
In fact, the centripetal force is the force that keeps the car in circular motion, and it points toward the centre of the circular trajectory. The frictional force between the tyres of the car and the road provides the centripetal force that keeps the car in the turn: in fact, without the friction (e.g. on an icy road), the car would not be able to make the turn at the same speed.
