**Core Concept**
Renal cell carcinoma (RCC) is a type of kidney cancer that arises from the renal epithelium. The management of RCC depends on the stage and resectability of the tumor. For surgically unresectable RCC, systemic therapy is the mainstay of treatment.

**Why the Correct Answer is Right**
Sunitinib is a multikinase inhibitor that targets vascular endothelial growth factor receptors (VEGFR), platelet-derived growth factor receptors (PDGFR), and other kinases involved in tumor angiogenesis. By inhibiting these receptors, sunitinib reduces tumor growth and metastasis. Sunitinib has been shown to improve survival and delay disease progression in patients with metastatic RCC.

**Why Each Wrong Option is Incorrect**
**Option A:** Bevacizumab is a monoclonal antibody that inhibits VEGF, but it is not the first-line treatment for unresectable RCC. Bevacizumab is often used in combination with other agents, such as interferon-alpha or chemotherapy.
**Option B:** Pazopanib is another multikinase inhibitor that targets VEGFR, PDGFR, and other kinases. While pazopanib is effective in RCC, it is not the preferred agent for unresectable disease due to its side effect profile and lower efficacy compared to sunitinib.
**Option C:** Interleukin-2 (IL-2) is an immunotherapy agent that has been used in the treatment of RCC, particularly in patients with metastatic disease. However, IL-2 is associated with significant toxicity and is not the preferred agent for unresectable RCC.

**Clinical Pearl / High-Yield Fact**
Sunitinib is a tyrosine kinase inhibitor that has been shown to improve survival in patients with unresectable RCC. It is essential to monitor patients on sunitinib for hand-foot syndrome, hypertension, and other adverse effects.

**Correct Answer: C. Sunitinib**