**Core Concept**
The question is testing the student's knowledge of mast cell stabilization, a mechanism used to prevent the release of inflammatory mediators such as leukotrienes and histamine. This concept is crucial in the management of allergic diseases like asthma and anaphylaxis.

**Why the Correct Answer is Right**
The correct answer is **C. Cromolyn sodium**. Cromolyn sodium works by stabilizing mast cell membranes, preventing the release of histamine and leukotrienes during an allergic reaction. This occurs through the inhibition of the calcium influx into mast cells, which is essential for the degranulation process. Cromolyn sodium binds to the calcium channels on the mast cell membrane, thereby blocking the entry of calcium ions and preventing the release of histamine and leukotrienes.

**Why Each Wrong Option is Incorrect**
**Option A:** **Zafirlukast** is a leukotriene receptor antagonist, not a mast cell stabilizer. It works by blocking the action of leukotrienes at their receptors, rather than preventing their release from mast cells.
**Option B:** **Fexofenadine** is an antihistamine that blocks the action of histamine at its receptors, but it does not prevent the release of histamine from mast cells.
**Option D:** **Montelukast** is another leukotriene receptor antagonist, similar to Zafirlukast, and does not prevent the release of leukotrienes from mast cells.

**Clinical Pearl / High-Yield Fact**
Cromolyn sodium is often used as a prophylactic agent in the management of allergic diseases, and it is particularly useful in preventing exercise-induced bronchospasm.

**Correct Answer:** C. Cromolyn sodium