**Core Concept**
Class III antiarrhythmic drugs are a group of medications that primarily prolong the action potential duration and refractory period in cardiac cells. They work by blocking potassium channels, which leads to an increase in the action potential duration and a decrease in the rate of repolarization.

**Why the Correct Answer is Right**
The mechanism of action of Class III antiarrhythmic drugs involves the blockade of potassium channels, specifically the slow delayed rectifier potassium channels (IKs) and the rapid delayed rectifier potassium channels (IKr). This blockade prolongs the action potential duration and refractory period, making it more difficult for arrhythmias to occur. Examples of Class III antiarrhythmic drugs include sotalol, amiodarone, and dofetilide.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Class I antiarrhythmic drugs primarily work by blocking sodium channels, not potassium channels.
**Option B:** This option is incorrect as Class II antiarrhythmic drugs primarily work by blocking beta-adrenergic receptors, not potassium channels.
**Option C:** This option is incorrect as Class IV antiarrhythmic drugs primarily work by blocking calcium channels, not potassium channels.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Class III antiarrhythmic drugs can increase the risk of torsades de pointes, a specific type of abnormal heart rhythm that can be life-threatening. This is because the blockade of potassium channels can lead to a prolonged QT interval and increased susceptibility to arrhythmias.

**Correct Answer: C. Amiodarone.**