## **Core Concept**
The question tests understanding of glucose metabolism, specifically the pathways of glycogenolysis and gluconeogenesis, and their role in maintaining blood glucose levels during fasting states. The child in the scenario likely suffers from a disorder affecting one of these pathways, leading to an inability to maintain glucose homeostasis.

## **Why the Correct Answer is Right**
The correct answer, Glucose-6-phosphatase, is crucial for the final steps of both glycogenolysis and gluconeogenesis, allowing glucose to be released into the bloodstream. This enzyme catalyzes the conversion of glucose-6-phosphate to glucose, which is then released into the blood. A deficiency in glucose-6-phosphatase leads to an inability to convert glucose-6-phosphate into glucose, thereby impairing the release of glucose into the bloodstream from glycogenolysis and gluconeogenesis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the enzyme described does not match the function related to the inability to utilize glucose from glycogenolysis or gluconeogenesis as described.
- **Option B:** This option is incorrect for similar reasons; the enzyme's deficiency does not lead to the specific metabolic block described in the question.
- **Option C:** This option is incorrect as it does not directly relate to the final step of glucose release into the bloodstream from glycogenolysis and gluconeogenesis.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that a deficiency in glucose-6-phosphatase is associated with **Von Gierke's disease (Type I Glycogen Storage Disease)**, characterized by severe hypoglycemia, lactic acidosis, and hepatomegaly due to the accumulation of glycogen and glucose-6-phosphate in the liver.

## **Correct Answer:** . Glucose-6-phosphatase