**Core Concept**
The treatment of choice for Stage I Wilm's Tumor involves a multi-disciplinary approach focusing on surgical removal of the tumor with the aim of preserving renal function and minimizing long-term sequelae. This approach typically involves a combination of chemotherapy and surgery.

**Why the Correct Answer is Right**
The preferred treatment for Stage I Wilm's Tumor is nephron-sparing surgery (NSS) or partial nephrectomy, which involves removing the tumor while preserving as much normal kidney tissue as possible. This approach is based on the principle of minimizing long-term renal function impairment in children. The role of chemotherapy in Stage I Wilm's Tumor is still debated, but it is often recommended for patients with aggressive histopathological features or those at high risk of relapse.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because radical nephrectomy, which involves complete removal of the kidney, is generally reserved for patients with more advanced disease or those who have undergone previous surgery.

**Option B:** This option is incorrect because chemotherapy alone is not sufficient for the treatment of Stage I Wilm's Tumor, as it is often used in conjunction with surgery.

**Option C:** This option is incorrect because radiation therapy is not typically used in the primary treatment of Wilm's Tumor, especially in children, due to the risk of long-term sequelae.

**Clinical Pearl / High-Yield Fact**
A key consideration in the treatment of Wilm's Tumor is the preservation of renal function, as these patients are at risk of developing chronic kidney disease and end-stage renal disease later in life.

**Correct Answer:** C. Nephron-sparing surgery (NSS) or partial nephrectomy.