What must a driver do when leaving a motor vehicle parked on a downhill slope (pendiente descendente)?

1. Turn the front wheels toward the curb (hacia la acera/cuneta) and engage reverse gear plus the parking brake
2. Turn the front wheels away from the curb toward the center of the street
3. Leave the gear in neutral and rely solely on the parking brake
4. Leave the engine idling to keep hydraulic brake pressure active