By law, a driver is responsible for ensuring that:

Answer: A — All passengers under the age of 16 wear a seatbelt

The law states that a driver is responsible for ensuring that all passengers under the age of 16 wear a seatbelt. This regulation is in place because younger passengers are more vulnerable in the event of a crash, and seatbelts significantly reduce the risk of injury or fatality. While some regulations may require different age limits, the specific responsibility lies with the driver to confirm that children up to that age are properly secured. This emphasizes the importance of passenger safety and the driver's role in upholding these laws. Ensuring seatbelt use among younger passengers both protects them and aligns with legal requirements aimed at improving overall road safety.