**Core Concept**
Long-acting beta 2 agonists (LABAs) are a class of medications used in the management of asthma and chronic obstructive pulmonary disease (COPD). They work by stimulating beta 2 receptors in the lungs, leading to bronchodilation and improved airflow. LABAs are designed to provide 12-24 hours of bronchodilation.

**Why the Correct Answer is Right**
Salmeterol is a specific example of a LABA. It has a slow onset of action but a long duration of effect, making it suitable for twice-daily dosing. Salmeterol binds to beta 2 receptors with high affinity, causing sustained bronchodilation. This is particularly useful for patients who require long-term control of their asthma or COPD symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Albuterol is a short-acting beta 2 agonist (SABA), used for quick relief of asthma symptoms. It has a rapid onset of action but a short duration of effect, typically requiring more frequent dosing.
**Option B:** Formoterol is a LABA, but it has a faster onset of action compared to salmeterol, making it more suitable for combination therapy with other medications.
**Option C:** Terbutaline is another SABA, often used in pregnancy for asthma exacerbations due to its safety profile.

**Clinical Pearl / High-Yield Fact**
Long-acting beta 2 agonists like salmeterol should be used in conjunction with inhaled corticosteroids (ICS) for optimal asthma control, as indicated in the Global Initiative for Asthma (GINA) guidelines.

**Correct Answer:** C. Salmeterol