**Core Concept**
The question is testing the student's knowledge of hereditary fructose intolerance (HFI), a rare genetic disorder caused by a deficiency of the enzyme aldolase B. Aldolase B is crucial for the breakdown of fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate in the liver, kidneys, and small intestine.

**Why the Correct Answer is Right**
Aldolase B deficiency leads to an inability to metabolize fructose, resulting in its accumulation in the body. When the child ingests fruit juice containing fructose, the accumulated fructose is toxic to the liver and kidneys, causing episodes of vomiting, hypoglycemia, and even liver failure. The deficiency of aldolase B is inherited in an autosomal recessive pattern, making it a concern for families with a history of HFI.

**Why Each Wrong Option is Incorrect**
**Option A:** Fructokinase is another enzyme involved in fructose metabolism, but its deficiency leads to essential fructosuria, a benign condition that does not cause symptoms like vomiting.
**Option B:** Glucose 6-phosphatase deficiency is associated with glycogen storage disease type I (von Gierke disease), which presents with hypoglycemia, lactic acidemia, and hepatomegaly, but not specifically with fructose intolerance.
**Option D:** Hexokinase is an enzyme that phosphorylates glucose to glucose-6-phosphate, and its deficiency is not directly related to fructose metabolism or hereditary fructose intolerance.

**Clinical Pearl / High-Yield Fact**
Hereditary fructose intolerance is often diagnosed in infancy or early childhood, but it can be challenging to diagnose due to its nonspecific symptoms. A high index of suspicion, particularly in children with a family history of HFI, is essential for early diagnosis and management.

**✓ Correct Answer: A. Aldolase**