Final answer:
A nurse should inform parents that breast milk is nutritionally complete for an infant up to 6 months of age and is ideally suited to support their growth and immune system.
Step-by-step explanation:
The correct statement that the nurse should make regarding breastfeeding is: "Breast milk is nutritionally complete for an infant up to 6 months of age." Breast milk, including colostrum, transitional milk, and mature milk, provides the necessary hydration, nutrients, and immunoglobulins to support an infant's growth and immune system during the first months of life. Cow's milk is not suitable for infants as it contains less lactose and fat and more protein and minerals, making it difficult for an infant's immature digestive system to metabolize. Furthermore, mature milk changes during feeding, offering foremilk to quench thirst and hindmilk to satisfy appetite.