**Core Concept**
Montelukast is a medication that leverages the body's natural inflammatory response to treat respiratory conditions. It specifically targets the leukotriene pathway, a crucial mediator of inflammation in asthma and allergic rhinitis.

**Why the Correct Answer is Right**
Montelukast is a selective cysteinyl leukotriene receptor antagonist (CysLT1 receptor antagonist). By blocking the action of cysteinyl leukotrienes (CysLTs) on the CysLT1 receptor, montelukast inhibits the pro-inflammatory effects of these mediators. This results in reduced airway inflammation, smooth muscle contraction, and mucus production, making it an effective treatment for asthma and other respiratory conditions.

**Why Each Wrong Option is Incorrect**
**Option A:** Montelukast is not a bronchodilator, as it does not directly relax airway smooth muscle.
**Option B:** Montelukast is not an anticholinergic, as it does not block the action of acetylcholine on muscarinic receptors.
**Option C:** Montelukast is not a corticosteroid, as it does not have systemic anti-inflammatory effects.

**Clinical Pearl / High-Yield Fact**
Montelukast is often used as add-on therapy in patients with asthma who remain symptomatic despite inhaled corticosteroids. It is also effective in treating seasonal allergic rhinitis and exercise-induced bronchospasm.

**Correct Answer:** C. Montelukast is a leukotriene receptor antagonist.