**Core Concept**
The Recommended Dietary Allowance (RDA) for infants refers to the optimal intake of Vitamin A, an essential nutrient crucial for vision, immune function, and skin health. Vitamin A deficiency can lead to night blindness and impaired immune responses, making it vital to ensure adequate intake.

**Why the Correct Answer is Right**
The RDA for Vitamin A in infants varies based on age and weight. Typically, the RDA for infants is around 300-400 μg/day. This is crucial for supporting the rapid growth and development of the infant's retina and immune system. Vitamin A is fat-soluble and requires adequate fat intake for absorption.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is lower than the RDA for infants, potentially leading to Vitamin A deficiency.
**Option B:** This option is incorrect as it is higher than the RDA for infants, potentially leading to Vitamin A toxicity.
**Option C:** This option is incorrect as it is not a standard unit of measurement for Vitamin A intake.

**Clinical Pearl / High-Yield Fact**
It is essential to note that excessive intake of Vitamin A can lead to toxicity, characterized by symptoms such as headache, dizziness, and liver damage. Therefore, it is crucial to adhere to the recommended dietary allowance.

**Correct Answer: C. 400 μg/day**