Final answer:
The cervical spine is most protected from whiplash injuries when the headrest is correctly positioned, as it limits the backward motion of the head during a collision.
Step-by-step explanation:
The cervical spine is most protected from whiplash-type injuries when the headrest is appropriately positioned. The anterior longitudinal ligament, which runs down the anterior side of the vertebral column, helps resist excess backward bending of the neck. A properly positioned headrest will restrict the backward motion of the head during a rear-end collision, thereby protecting the cervical spine from injury. While airbags can minimize serious injuries and are important safety features, the direct prevention of whiplash is more correlated with the headrest's position. Tensing up at the time of impact or the vehicle being struck from the rear are factors that are less controllable and can vary in their impact on injury severity.