## Core Concept
The question revolves around a bodybuilder who develops fatigue on moderate exercise after consuming raw eggs as a protein source. This scenario suggests a nutritional deficiency likely caused by a component in raw eggs. The prescribed vitamin hints at a specific enzymatic deficiency related to energy metabolism.

## Why the Correct Answer is Right
The correct answer, **B. Biotinidase**, is related to the condition caused by consuming raw eggs. Raw eggs contain a protein called **avidin**, which tightly binds to **biotin**, a B-vitamin essential for various metabolic processes, including energy production. Biotinidase is the enzyme responsible for recycling biotin from dietary sources. A deficiency in biotinidase leads to **biotin deficiency**, which can cause fatigue, skin rashes, and neurological symptoms. When the bodybuilder started consuming raw eggs, the avidin in the eggs bound to biotin, making it unavailable for the body, and the existing biotinidase deficiency worsened, leading to symptoms like fatigue on moderate exercise.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not directly relate to the scenario described. Without specifying the enzyme, it's hard to directly refute, but given the context, it's less likely related to biotin metabolism or the specific issue of consuming raw eggs.
- **Option C:** This option is incorrect as it does not specify an enzyme related to the described condition. The focus is on biotin metabolism given the context.
- **Option D:** This option is incorrect because it does not directly relate to the enzymatic deficiency implied by the scenario.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **avidin in raw eggs can lead to biotin deficiency** if a significant amount of raw eggs is consumed regularly. This is a classic example of how diet can lead to specific vitamin deficiencies, and it's crucial for individuals, especially those on unusual diets, to be aware of potential nutritional deficiencies.

## Correct Answer Line
**Correct Answer: B. Biotinidase**.