Final answer:
d. A child walks down stairs by placing both feet on one step. The school nurse is most concerned if a child walks down stairs by placing both feet on one step. This indicates a delay in gross motor skills development and could be a cause for concern.
Step-by-step explanation:
The school nurse is most concerned if a child walks down stairs by placing both feet on one step. By age five, children should be able to walk up and down stairs using alternating feet, one step at a time while holding on to a rail or someone's hand. Placing both feet on one step indicates a delay in gross motor skills development, which could be a cause for concern. The ability to walk up and down stairs correctly is an important milestone in a child's physical development and should be achieved by kindergarten age.