An 18-Month-Old Child Has Horizontal, Bright White Lines Along the Upper

An 18-month-old child has horizontal, bright white lines along the upper gum line of the teeth. What is the most important question the primary care pediatric nurse practitioner will ask the child's parents?

A) If the child is still drinking milk from a bottle
B) If the child or the parents are brushing the teeth
C) If they are brushing the child's teeth twice daily
D) If they have taken the child to a dentist