A nurse is counseling parents of a 9-month-old infant who is currently breastfed and beginning complementary foods. The parents ask when it is safe to replace breast milk or formula with whole cow's milk. Based on the infant's developmental stage and nutritional needs, what should the nurse advise?

Introduce whole cow's milk at 9 months since the infant is already starting solids.

Introduce whole cow's milk at 6 months of age along with complementary foods.

Introduce whole cow's milk at 12 months of age to prevent kidney stress and iron deficiency.

Introduce whole cow's milk as soon as the infant shows readiness for self-feeding, regardless of age.