(A) is wrong because we're not concerned about parents who don't have child safety seats, we're concerned about the ones who do use them, but still have children who are injured.
(B) is wrong because it still doesn't explain the fact that the children are receiving injuries that the safety seats were specifically designed to avoid.
(C) is wrong for the same reason as (A).
(D) is wrong because it's still surprising that children are still sustaining the types of injuries that safety seats were specifically designed to avoid.
