**Core Concept**
Fructose intolerance is a condition where the body is unable to properly metabolize fructose, a simple sugar found in many fruits and table sugar. This intolerance is caused by a deficiency in the enzyme responsible for breaking down fructose in the liver.

**Why the Correct Answer is Right**
The correct answer is Aldolase B, a fructose-metabolizing enzyme that catalyzes the breakdown of fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate. This enzyme is crucial for the proper metabolism of fructose in the liver. A deficiency in Aldolase B leads to a buildup of fructose-1-phosphate, causing a range of symptoms including nausea, vomiting, and diarrhea. This condition is known as hereditary fructose intolerance.

**Why Each Wrong Option is Incorrect**

**Option B:** Fructokinase is another enzyme involved in fructose metabolism, but it catalyzes the phosphorylation of fructose to form fructose-1-phosphate. A deficiency in fructokinase leads to a different condition known as essential fructosuria, which is generally benign and does not cause symptoms.

**Option C:** Triokinase is an enzyme that catalyzes the conversion of glyceraldehyde to glyceraldehyde-3-phosphate, a step in the glycolytic pathway. However, it is not directly involved in fructose metabolism and is not responsible for fructose intolerance.

**Option D:** Aldolase A is an enzyme involved in glycolysis, catalyzing the conversion of fructose-1,6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. It is not directly involved in fructose metabolism and is not responsible for fructose intolerance.

**Clinical Pearl / High-Yield Fact**
Hereditary fructose intolerance is a rare genetic disorder caused by a deficiency in Aldolase B. It is essential to recognize this condition, as it can be managed with a strict fructose-free diet.

**✓ Correct Answer: A. Aldolase B**