What should head rests be adjusted to contact in order to prevent neck injuries if you are hit from behind?

Answer: B — The back of the head

Headrests should be adjusted to contact the back of the head to prevent neck injuries in case of a rear-end collision. This positioning helps in reducing the risk of whiplash by providing support to the head and neck during an impact. Adjusting the headrest to the proper height ensures that it can effectively absorb and distribute the energy generated during a collision, protecting the neck from sudden, jolting movements. The other options are incorrect as they do not provide the necessary support and protection needed in the event of a rear-end collision.