**Core Concept**
Human milk is a complex mixture of nutrients, antibodies, and bioactive molecules that provide optimal nutrition for infants. The composition of human milk differs significantly from cow's milk, which is a common dairy product consumed by humans. The comparison of nutrient levels between human milk and cow's milk is essential for understanding the unique nutritional requirements of infants.

**Why the Correct Answer is Right**
Human milk contains a higher concentration of **Lactoferrin**, a glycoprotein with antimicrobial, anti-inflammatory, and immunomodulatory properties. Lactoferrin is essential for protecting infants from infections and promoting the development of their gut microbiota. In contrast, cow's milk contains relatively low levels of lactoferrin. This difference in lactoferrin content highlights the unique nutritional profile of human milk, which is tailored to meet the specific needs of human infants.

**Why Each Wrong Option is Incorrect**
**Option A:** **Calcium** is actually present in higher concentrations in cow's milk compared to human milk.
**Option B:** **Vitamin D** is also more abundant in cow's milk than in human milk.
**Option C:** **Potassium** levels are similar in both human milk and cow's milk.

**Clinical Pearl / High-Yield Fact**
Human milk is a dynamic fluid that changes in composition in response to the infant's nutritional needs and environmental factors. It is essential for healthcare providers to understand the unique properties of human milk and its benefits for infant health.

**Correct Answer:** C. Potassium