**Core Concept**
Pulse deficit refers to the difference between the apical and radial pulse rates, indicating an irregular heartbeat. Atrial fibrillation is a type of supraventricular tachycardia characterized by rapid and irregular atrial contractions, disrupting normal cardiac rhythm.

**Why the Correct Answer is Right**
In atrial fibrillation, the atria contract rapidly and irregularly, resulting in a rapid and irregular ventricular rate. This irregularity leads to a pulse deficit, as the ventricles are not able to maintain a consistent contraction rate. The pulse deficit in atrial fibrillation is typically more than 10 beats per minute due to the irregular atrial contractions. The heart rate in atrial fibrillation is often between 100-160 beats per minute, leading to a significant pulse deficit.

**Why Each Wrong Option is Incorrect**
**Option A:** Ventricular premature contractions (VPCs) can cause irregularities in the cardiac rhythm, but they do not typically result in a significant pulse deficit of more than 10 beats per minute. VPCs are usually isolated events and do not disrupt the normal cardiac rhythm as much as atrial fibrillation.
**Option B:** Atrial flutter is a type of supraventricular tachycardia characterized by a rapid and regular atrial contraction rate. While it can cause a pulse deficit, it is typically less than 10 beats per minute, as the atrial contractions are regular and synchronized.
**Option D:** Ventricular fibrillation is a life-threatening condition characterized by a rapid and irregular ventricular contraction rate. However, it is usually associated with a slow pulse or no palpable pulse, rather than a significant pulse deficit.

**Clinical Pearl / High-Yield Fact**
A pulse deficit of more than 10 beats per minute is highly suggestive of atrial fibrillation. This is a classic clinical finding that can help diagnose this condition, especially in patients with a rapid and irregular heartbeat.

**✓ Correct Answer: C. Atrial fibrillation**