## **Core Concept**
The question tests knowledge of beta blockers, specifically their duration of action. Beta blockers are a class of medications that inhibit the effects of **beta-adrenergic receptors**, which are part of the sympathetic nervous system. They are primarily used to treat cardiovascular diseases such as hypertension, heart failure, and angina.

## **Why the Correct Answer is Right**
Sotalol is known for its long duration of action among beta blockers. It is a **non-selective beta blocker** with additional properties as a **class III antiarrhythmic agent**, which means it also blocks potassium channels. This unique profile makes it useful for treating certain types of arrhythmias. Its long half-life allows for once or twice daily dosing, contributing to its classification as a long-acting beta blocker.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While propranolol is a non-selective beta blocker, it is not classified as the longest-acting beta blocker. It has a half-life that can vary but generally requires multiple daily doses.
- **Option B:** Metoprolol is a selective β1 beta blocker with a moderate duration of action, not considered long-acting compared to sotalol. It typically requires twice daily dosing.
- **Option C:** Atenolol is another selective β1 beta blocker, known for its relatively long half-life, which allows for once daily dosing. However, its duration of action is not as long as sotalol's.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **sotalol** stands out due to its unique combination of beta-blocking and class III antiarrhythmic properties, making it particularly useful in managing certain arrhythmias. Its long half-life, which can range approximately from 12 to 20 hours, supports once or twice daily dosing.

## **Correct Answer:** D. Sotalol.