Final answer:
Babies must not ride facing forward until they are at least 1 year old and weigh 20 pounds, as rear-facing car seats offer the necessary protection for their still-developing head, neck, and spine.
Step-by-step explanation:
Babies must not ride facing forward in a car seat until they are 1 year old and weigh at least 20 pounds. It is essential for babies' safety to ride in a rear-facing car seat in the back until they reach this milestone. This helps protect a baby's head, neck, and spine in the event of a car accident, which is crucial since these areas are especially vulnerable at a young age. Babies go through significant development in their first year, including gaining the muscle strength to sit up, crawl, and eventually stand. However, despite these milestones, their bodies are not yet prepared for the impact of a forward-facing car seat in a vehicle.