How is a driver required to adjust the vehicle’s head rest?

1. A The upper edge of the head-rest should be aligned with the bottom line of the driver’s neck.
2. B The lower edge of the head-rest should be aligned with the upper tip of the driver’s head.
3. C The upper edge of the head-rest should be aligned with the upper tip of the driver’s head.
4. D Proper adjustment of the driver’s head-rest is of no significance.