How must children under 12 years be secured in a vehicle?

Children under 12 years must be secured in a vehicle using an appropriate child safety seat or booster. This requirement is based on ensuring that young passengers are properly protected while traveling, as their bodies are not fully developed to safely use adult seatbelts.

Child safety seats and boosters are designed to accommodate the specific sizes and weights of children, providing better protection in the event of a crash. They help position the vehicle's seatbelt correctly across the child's body, which is crucial for minimizing the risk of injury. Additionally, using age-appropriate restraints significantly enhances the safety of younger passengers.

The other options do not provide the necessary level of protection for children. For instance, using a seatbelt only without a booster seat may not fit properly, and having a child sit in the front passenger seat increases the risk of injury from airbags and the dashboard. Similarly, allowing a child to use a regular adult seat does not offer the appropriate safety measures designed for their age and size. Adhering to the proper use of child safety seats and boosters helps to ensure that children travel as safely as possible in any vehicle.