What is the primary purpose of a seatbelt?

The primary purpose of a seatbelt is to protect the occupants in the vehicle during a collision. Seatbelts are designed to restrain individuals against the forces of impact, thereby reducing the risk of injury or death in the event of a crash. In a collision, unrestrained passengers can be thrown forward, leading to severe injuries from both the impact and from colliding with the vehicle's interior or other passengers.

By securely holding passengers in place, seatbelts help to distribute the forces of a crash across stronger parts of the body, reducing the likelihood of serious injury. They also prevent ejection from the vehicle, which is one of the most dangerous scenarios during an accident. The effectiveness of seatbelts is supported by extensive research and crash statistics, which show that wearing a seatbelt significantly decreases the chances of fatalities and severe injuries in accidents.

Other options do not reflect the primary function of a seatbelt. While seatbelts may contribute marginally to comfort or posture, their critical role is safety during a collision, making option B the correct answer.