Question

the total number of occupants in a vehicle driven by someone with a probationary license may not exceed the number of installed seat belts head restraints bench seats

Explanation:

This question is about traffic regulations, specifically regarding the number of occupants allowed in a vehicle driven by someone with a probationary license. The key point is that the number of occupants should not exceed the number of installed seat belts, as seat belts are required for each occupant's safety and are the standard measure for determining the maximum number of people a vehicle can legally carry. Head restraints are for neck support and not related to occupant count, and bench seats are a type of seating but don't determine the legal limit—seat belts do.

Answer:

A. seat belts