Final answer:
Children ages 0 to 2.5 years must be in a rear-facing car seat, children 2.5 to 6 years in a forward-facing car seat, and children 6 to 13 years in a booster seat until they fit an adult seat belt correctly.
Step-by-step explanation:
The question pertains to the regulations regarding the age at which a child needs to be positioned in a car seat or booster seat when a rear seat is available in a vehicle. Among the options provided, the correct one must align with safety guidelines that are generally recommended by child safety and vehicular safety authorities.
However, the actual age may vary depending on specific state laws. Generally, it is recommended that children ages 0 to 2.5 years must be in a rear-facing car seat, children ages 2.5 to 6 years should be in a forward-facing car seat, and children ages 6 to 13 years should be using a booster seat until they are big enough to fit an adult seat belt properly.