A 6-year-old boy presents with failure to thrive, recurrent sinopulmonary infections, and bulky, foul-smelling stools despite adequate caloric intake. Vital signs show HR 110/min, RR 28/min, SpO2 92% on room air, and temperature 37.2°C. Chest X-ray reveals hyperinflation with bronchial wall thickening. Fecal fat is elevated at 8 g/day. He denies recent antibiotic use. Genetic analysis confirms the most common cystic fibrosis mutation. Which molecular defect does this mutation cause?

1. A)Defective receptor tyrosine kinase signaling
2. B)Misfolding with impaired protein trafficking to the cell surfaceGABARITO
3. C)Reduced synthesis of surfactant phospholipids
4. D)Premature truncation of a mitochondrial membrane protein
5. E)Abnormal collagen cross linking in the extracellular matrix