Under what condition can a child sit in the front seat if all rear seats are unavailable?

The correct answer is based on safety guidelines regarding child passengers in vehicles. Specifically, a child can sit in the front seat if they are in a rear-facing position with the airbag deactivated. This is crucial because rear-facing seats provide the best protection for young children during a crash, as they are designed to support the head, neck, and spine. Deactivating the airbag is necessary because airbags can be dangerous for rear-facing children in the event of a collision; they deploy with significant force that can injure a child in that position.

While other options mention using a booster seat, wearing a seatbelt, or being a certain age, they do not align with the best practices for child safety in vehicles. A booster seat is intended for older children who have outgrown a forward-facing seat but are still not tall enough for an adult seatbelt to fit properly. Simply wearing a seatbelt does not ensure the safety of a younger child who is not properly secured in an age-appropriate restraint. Additionally, age alone, like being at least 10 years old, does not address the many other factors involved in child passenger safety who may still require a child safety seat.