**Core Concept**
Sarcoidosis is a multisystem granulomatous disorder that can affect various organs, including the lungs, skin, and heart. The involvement of the heart, particularly the conduction system, can lead to life-threatening arrhythmias.

**Why the Correct Answer is Right**
The most common cause of sudden death in sarcoidosis is cardiac tamponade due to cardiac involvement, particularly pericardial involvement. This occurs when the granulomatous inflammation leads to scarring and thickening of the pericardium, resulting in impaired cardiac filling and ultimately cardiac tamponade. The cardiac tamponade can be exacerbated by the presence of cardiac arrhythmias, such as atrioventricular block, which can further compromise cardiac function.

**Why Each Wrong Option is Incorrect**
**Option A:** Cardiac arrhythmias are a potential complication of sarcoidosis but are not the most common cause of sudden death.
**Option B:** Pulmonary involvement is a common feature of sarcoidosis, but it is not typically associated with sudden death.
**Option C:** Neurosarcoidosis can cause a range of neurological symptoms, but it is not the most common cause of sudden death in sarcoidosis.

**Clinical Pearl / High-Yield Fact**
Sarcoidosis can cause cardiac involvement in up to 5% of patients, often presenting with arrhythmias or cardiac tamponade, highlighting the importance of cardiac monitoring in patients with known sarcoidosis.

**Correct Answer:** D.