What is the function of the headrest of your vehicle's seat?

What is the function of the headrest of your vehicle's seat?
A)To be more comfortable on long journeys and be able to drive longer without stopping.
B)To prevent whiplash in rear-end collisions.Correct
C)To prevent the head from moving while we drive.
The headrest will have the function of preventing the sudden backward movement of the head and the resulting whiplash, in the event of a rear-end collision.
For it to be correctly adjusted:
- Height: the upper part of the headrest must be placed at the same height as the upper part of the head (its widest part should be at eye level).
- Distance: the gap between the head and the headrest must be as small as possible (never greater than 4 cm).