What is the purpose of a seat belt?

The primary purpose of a seat belt is to protect occupants in the event of a collision. When a vehicle is involved in an accident, the sudden deceleration can cause unrestrained passengers and drivers to continue moving forward at high speeds. Seat belts are designed to hold passengers in their seats, minimizing the risk of serious injury by preventing ejection from the vehicle and reducing the movement of the body in relation to the vehicle's interior. This protective measure significantly increases the chances of surviving a crash and decreases the severity of injuries sustained.

The other choices touch on related concepts, but they do not encompass the main function of seat belts. While holding passengers in place during acceleration might be a benefit, it is not the primary safety function. Keeping the driver from leaving the seat and preventing passengers from opening doors are aspects of vehicle operation and safety but do not relate directly to the crucial protective purpose of seat belts during crashes.