**Core Concept**
Cystic fibrosis is a genetic disorder affecting the exocrine glands, particularly the pancreas, lungs, and liver, due to mutations in the CFTR gene. This leads to abnormal chloride transport across epithelial membranes, resulting in thickened secretions and subsequent glandular dysfunction.

**Why the Correct Answer is Right**
The CFTR gene encodes for the cystic fibrosis transmembrane conductance regulator protein, a chloride channel responsible for maintaining the balance of chloride ions across epithelial cell membranes. In cystic fibrosis, mutations in the CFTR gene lead to defective chloride transport, causing the production of thick, sticky mucus that clogs the airways and traps bacteria, leading to recurrent respiratory infections. The abnormal secretions also impair pancreatic enzyme secretion, resulting in malabsorption and failure to thrive.

**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect as it does not relate to the underlying pathophysiology of cystic fibrosis.
**Option B:** This option is also incorrect, as it is not directly related to the genetic or molecular basis of cystic fibrosis.

**Clinical Pearl / High-Yield Fact**
Cystic fibrosis is an autosomal recessive disorder, meaning that a child must inherit two defective copies of the CFTR gene (one from each parent) to express the disease. This highlights the importance of genetic counseling for families with a history of cystic fibrosis.

**Correct Answer:** C. The basic abnormality in this infant involves defective chloride transport due to mutations in the CFTR gene.