**Core Concept**
The child's symptoms of greasy and pungent bowel movements, combined with respiratory distress and a positive sweat-chloride test, suggest a diagnosis of cystic fibrosis (CF). CF is a genetic disorder characterized by abnormal sweat gland function, leading to elevated sweat chloride levels. The disease is caused by mutations in the CFTR gene, which encodes a chloride channel responsible for maintaining proper fluid balance in the body.

**Why the Correct Answer is Right**
The correct answer, "Lack of pancreatic enzyme secretion," is due to the abnormal function of the CFTR protein in the pancreas. Normally, the CFTR protein helps regulate the flow of chloride ions into the pancreatic ducts, allowing for proper digestion and absorption of nutrients. In CF, the mutated CFTR protein leads to a buildup of thick, sticky mucus in the pancreas, causing a lack of pancreatic enzyme secretion into the intestine. This results in malabsorption of fats and fat-soluble vitamins, leading to steatorrhea (greasy bowel movements).

**Why Each Wrong Option is Incorrect**
**Option A:** Abnormal dietary intake is unlikely to cause steatorrhea in this child, as the disease is likely related to a genetic disorder rather than dietary habits.

**Option B:** Bacterial overgrowth is not directly related to the symptoms of steatorrhea and respiratory distress in this child, and is not the primary cause of the disease.

**Option C:** Hyperbilirubinemia with kernicterus is a condition related to jaundice and brain damage in newborns, and is not related to the symptoms of steatorrhea and respiratory distress in this child.

**Clinical Pearl / High-Yield Fact**
The sweat-chloride test is a crucial diagnostic tool for cystic fibrosis, as elevated sweat chloride levels are a hallmark of the disease. This test can help distinguish CF from other causes of respiratory distress and malabsorption.

**✓ Correct Answer: D. Lack of pancreatic enzyme secretion**