Final answer:
Modern seat belts are three-point lap and shoulder safety belts that are passive restraint devices. They should fit somewhat loosely across the chest.
Step-by-step explanation:
Modern seat belts are three-point lap and shoulder safety belts, which means they have a strap that goes across the lap and another strap that goes diagonally across the chest and over the shoulder. They are considered passive restraint devices because they automatically engage in the event of a sudden stop or collision without the need for the driver to actively fasten them. Seat belts should fit somewhat loosely across the chest to allow for movement and comfort while still providing the necessary safety.