In a car equipped with rear seat belt, a child under 8 years old in the rear seat should

What this question teaches

For the question "In a car equipped with rear seat belt, a child under 8 years old in the rear seat should", the correct answer is "use a child restraint." because seat-belt and child-restraint rules are legal safety requirements, so the right answer is the one that matches the stated rule; the other choices such as "sit between adult passengers." and "have a soft cushion behind him/her." do not fit the rule as well.