Final answer:
Mandatory seat belt laws likely predate the 1991 requirement for airbags in vehicles, as seat belts are a fundamental safety feature in automobiles to prevent injuries.
Step-by-step explanation:
The information provided suggests that seat belts and airbags are safety features designed to minimize injuries during vehicle accidents. Airbags have been required in passenger vehicles in the United States since 1991, and it's implied that seat belts are also a required safety feature. Although no specific year is given for the seat belt requirement, it would be reasonable to assume that mandatory seat belt laws were enacted prior to the introduction of airbags, as seat belts are the more fundamental safety feature. Seat belts help to distribute the forces experienced in a crash across the stronger parts of one's body. This is crucial as it reduces the likelihood of injury or death in the event of a sudden stop or impact.