Step 1: Concept
Maternal milk provides both nutritional and immunological benefits that commercial formulas cannot fully replicate.
Step 2: Meaning
Antibodies (Immunoglobulins) are proteins that help the body fight off viruses and bacteria.
Step 3: Analysis
Formulas can be fortified with vitamins, proteins, and minerals. However, they lack the live biological components like antibodies (especially IgA) that are passed from mother to infant to build immunity.
Step 4: Conclusion
The absence of antibodies is the primary reason milk substitutes are considered inferior to breast milk.
Final Answer: (D)