Which of the mentioned body parts is the headrest on the vehicle seat designed to protect?

In the photo you can see the headrest of a car's front seat. The headrest is meant to protect the cervical spine - answer A. The frontal bone (B) and the occipital bone (C) are bones of the skull; the headrest does touch the back of the head, but its job is not to protect the bones of the head, but to stop the head moving backwards, so that the neck is not injured. The seat belt and the airbag protect you from hitting the interior with your forehead.

The Regulation on the technical conditions of vehicles requires a passenger car to have headrests on each outer front seat. When the car is hit from behind, the body held by the belt moves forward together with the seat, and the head, because of inertia, stays behind and snaps backwards - this is the so-called whiplash injury, which damages the vertebrae and ligaments of the neck even in a minor collision at a speed of 20-30 km/h. The headrest stops the head before the neck is bent too far. It works only when it is set correctly: its top edge should be at the height of the top of your head, and the distance from the back of your head should be as small as possible, at most a few centimetres. Before driving you adjust the headrest to your height, just like the seat and mirrors.

Legal basis: § 11 para. 1 point 9 of the Regulation on the technical conditions of vehicles and the scope of their necessary equipment