**Core Concept**
Leukotriene receptor antagonists are a class of medications used to manage symptoms of bronchial asthma by blocking the action of leukotrienes, which are potent inflammatory mediators involved in the pathogenesis of asthma. These medications work by inhibiting the cysteinyl leukotriene receptor 1 (CysLT1 receptor), thereby reducing airway inflammation and hyperresponsiveness.

**Why the Correct Answer is Right**
Montelukast, a leukotriene receptor antagonist, is specifically designed to bind to the CysLT1 receptor, preventing the action of leukotrienes such as LTC4, LTD4, and LTE4. This blockade results in decreased mucus production, reduced airway smooth muscle contraction, and decreased inflammation in the airways, making it an effective treatment for bronchial asthma. Montelukast is often used as an add-on therapy to inhaled corticosteroids in patients with persistent asthma.

**Why Each Wrong Option is Incorrect**
**Option A:** Zafirlukast - While zafirlukast is also a leukotriene receptor antagonist, it is not the most commonly used medication for bronchial asthma.

**Option B:** Ciclesonide - Ciclesonide is a corticosteroid used in the treatment of asthma, but it is not a leukotriene receptor antagonist.

**Option C:** Fluticasone - Fluticasone is a corticosteroid used in the treatment of asthma, but it is not a leukotriene receptor antagonist.

**Option D:** Zileuton - Zileuton is a leukotriene synthesis inhibitor, not a leukotriene receptor antagonist.

**Clinical Pearl / High-Yield Fact**
Leukotriene receptor antagonists, such as montelukast, are often used as add-on therapy in patients with persistent asthma, and they can be particularly useful in patients who experience nocturnal symptoms or exercise-induced bronchospasm.

**Correct Answer:** C. Montelukast