**Core Concept**
Anti-arrhythmic drugs are a class of medications used to treat abnormal heart rhythms (arrhythmias). They work by modulating the electrical activity of the heart through various mechanisms, including blocking sodium channels, potassium channels, or calcium channels.

**Why the Correct Answer is Right**
The correct answer is lidocaine, which is a class Ib anti-arrhythmic drug. Lidocaine works by blocking sodium channels, which reduces the automaticity of the heart and prevents the spread of abnormal electrical impulses. This results in a decrease in the frequency and severity of arrhythmias.

* **Mechanism of action**: Lidocaine inhibits the sodium channels in the heart, which reduces the rate of depolarization and prevents the spread of abnormal electrical impulses.
* **Clinical use**: Lidocaine is commonly used to treat ventricular arrhythmias, such as ventricular tachycardia and ventricular fibrillation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify an anti-arrhythmic drug.
* **Option B:** This option is incorrect because it does not name a specific anti-arrhythmic drug.
* **Option C:** This option is incorrect because it is not a commonly used anti-arrhythmic drug.

**Clinical Pearl / High-Yield Fact**
Lidocaine is often used in emergency situations to treat severe arrhythmias, but it can also cause central nervous system toxicity, including seizures and respiratory depression, especially at high doses.

**Correct Answer: D. Lidocaine**