The correct answer to this question is A, and they are not necessary if your vehicle has an airbag. All cards should have an airbag, but if they don't, a seat belt will still be required to wear. It saves lives every day. It was patented in 1959 by Volvo but sold the idea to Nils Bohlin who perfected it to the seatbelts we know today.
About 35 lives are saved every day with belts. They keep people from ejecting the vehicle when a crash occurs. Many states have seatbelt laws which require them to be worn when the vehicle is in use, and more people are wearing more seatbelts today.