**Core Concept:** Cystic fibrosis (CF) is a genetic disorder affecting the lungs, pancreas, and other organs due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Inhaled agents like mucolytics help dissolve the thick, sticky mucus in the airways, allowing for easier clearance of secretions and preventing airway obstruction and infection. One such mucolytic agent is dornase alfa, which is a recombinant DNA molecule that degrades extracellular DNA in the mucus.

**Why the Correct Answer is Right:** Dornase alfa (Option D) is an effective mucolytic agent used to dissolve cystic fibrosis-related mucus. It is a recombinant DNA molecule that contains an exo-nuclease enzyme, which breaks down extracellular DNA within the mucus, making it easier for the child to clear the mucus and prevent respiratory complications.

**Why Each Wrong Option is Incorrect:**

A. Salbutamol (Option C) is a beta-2 agonist used for bronchodilation and is not indicated for mucus clearance in cystic fibrosis. It is primarily used in asthma and chronic obstructive pulmonary disease (COPD).

B. Corticosteroids (Option B) are anti-inflammatory agents used in asthma and COPD to reduce airway inflammation. They are not indicated for mucus clearance in cystic fibrosis.

Epinephrine (Option A) is a sympathomimetic amine used for bronchodilation and is not indicated for mucus clearance in cystic fibrosis. It is primarily used in anaphylaxis and asthma.

**Clinical Pearl:** In cystic fibrosis, the use of dornase alfa alongside bronchodilators and antibiotics can lead to significant improvements in lung function and disease progression. It is crucial to tailor treatment to the individual patient's clinical presentation and disease severity.