How can a seat belt prevent injuries to the head and neck during a crash?

A seat belt is designed to restrain the occupant in their seat during a crash, effectively keeping them in a fixed position. This is crucial for minimizing movement of the body, especially the head and neck, which are particularly vulnerable to injury in a collision. When a vehicle experiences a sudden stop or an impact, unrestrained occupants can collide with the interior of the vehicle or experience whiplash due to rapid acceleration and deceleration of their head relative to the torso. By securing the occupant in place, a seat belt reduces the likelihood of such injuries and helps distribute the force of the crash across the stronger parts of the body, thereby reducing the risk of serious head and neck injuries.

The other options do not align with the primary protective function of a seat belt during a crash. For instance, allowing free movement of the head could lead to increased risk of injury due to the forces encountered in a collision, while providing a cushion between the passenger and the dashboard is not the primary role of a seat belt. Furthermore, enhancing the driver's visibility is not related to injury prevention during a crash; it pertains to safe driving practices rather than occupant protection during a collision.