Concept:
Human milk differs significantly from cow milk in composition, especially in free amino acids important for infant development.
Step 1: Free amino acids.
Human milk contains:
• Taurine (important for brain development)
Step 2: Role of taurine.
• Essential for infants
• Supports nervous system development
Step 3: Absence in cow milk.
Cow milk has negligible taurine.
Step 4: Conclusion.
Thus, taurine is the correct answer.