**Core Concept**
Scleroderma renal crisis (SRC) is a life-threatening complication of systemic sclerosis characterized by rapidly progressive renal failure, often associated with hypertension. The pathophysiology involves renal vasoconstriction and thrombosis due to endothelial injury, leading to acute kidney injury.

**Why the Correct Answer is Right**
The drug of choice for SRC is angiotensin-converting enzyme (ACE) inhibitor, which helps to reduce blood pressure, improve renal perfusion, and prevent further endothelial damage. ACE inhibitors block the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, thereby improving renal blood flow and reducing proteinuria.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because vasopressors are actually contraindicated in SRC, as they can exacerbate vasoconstriction and worsen renal perfusion.
* **Option B:** This option is incorrect because beta-blockers may be used to control hypertension in SRC, but they are not the primary treatment and can even worsen renal perfusion in the setting of ACE inhibitor therapy.
* **Option C:** This option is incorrect because calcium channel blockers may be used as an alternative to ACE inhibitors in some cases, but they are not the first-line treatment for SRC.

**Clinical Pearl / High-Yield Fact**
ACE inhibitors are the mainstay of treatment for scleroderma renal crisis, and their initiation is often life-saving. It is essential to monitor renal function and blood pressure closely in these patients.

**Correct Answer:** C.