## **Core Concept**
The question assesses knowledge of the antimicrobial properties present in milk, which provide protection to infants. Various components in milk have been identified to have direct or indirect anti-infective properties.

## **Why the Correct Answer is Right**
Lactoferrin, lysozyme, and nucleotides have documented anti-infective properties in milk. Lactoferrin binds to iron, making it unavailable for bacterial growth, and also has direct antimicrobial effects. Lysozyme is an enzyme that breaks down bacterial cell walls, exhibiting bacteriolytic activity. Nucleotides can influence immune system function and have been suggested to have roles in anti-infective defense. Lactalbumin, while a major protein in milk, does not have well-documented direct anti-infective properties like the others.

## **Why Each Wrong Option is Incorrect**
- **Option B: Lactalbumin** - This is a major protein in milk but does not have direct anti-infective properties attributed to it like lactoferrin, lysozyme, or specific roles like nucleotides.
- **Option A: Lactoferin** - Has anti-infective properties by depriving bacteria of iron necessary for their growth.
- **Option C: Lysozyme** - Directly breaks down bacterial cell walls, exhibiting anti-infective properties.
- **Option D: Nucleotides** - Have roles in enhancing the immune system and thus can be considered to have indirect anti-infective effects.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that breast milk provides newborns with significant protection against infections, partly due to these anti-infective properties. Among these, lactoferrin and lysozyme are well-known for their direct actions against pathogens.

## **Correct Answer:** B. Lactalbumin