A cohort study finds lower rates of gastrointestinal and respiratory infections among exclusively breastfed infants during the first 6 months compared to formula-fed infants. Which combination of mechanisms best explains these observed differences?

• A. Sterile packaging of formula increases infection risk because its minerals chelate with antibodies in the infant gut, preventing endogenous immunity from developing in neonates who do not receive breast milk.
• B. Higher bioavailability of certain nutrients in human milk plus transfer of maternal antibodies and immune cells that provide pathogen-specific protection and reduce allergy risk.
• C. Higher caloric density in breast milk compared with formula combined with greater protein content in formula that paradoxically increases susceptibility to infection by modulating infant gut pH.
• D. Formula contains live bacterial cultures that compete with the infant’s immune system, while breast milk lacks any antimicrobial factors, making breastfed infants less dependent on adaptive immunity.

Answer: (B)