**Core Concept:** Squamous cell carcinoma (SCC) is a malignant neoplasm that arises from squamous cells, primarily found in the skin and mucous membranes. In this question, the focus is on oral tongue SCC, which indicates a neoplasm developing in the squamous cells of the oral tongue.

**Why the Correct Answer is Right:**

The correct answer, **C. Radical neck dissection (RND)**, is chosen because it addresses the disease's advanced stage and potential for lymph node involvement in the neck. In advanced oral tongue squamous cell carcinoma, regional lymph node involvement (N+ staging) is common. RND is a surgical procedure that aims to remove all potentially involved lymph nodes (levels II to V) in the neck, ensuring complete removal of the primary tumor and regional spread.

**Why Each Wrong Option is Incorrect:**

A. **Mandibulectomy (removal of the mandible)** - This option is incorrect due to the extensive tissue removal and poor functional outcome, especially considering the patient's age and the possibility of regional lymph node involvement.

B. **Adjuvant radiotherapy (RT)** - While RT is a treatment option for oral tongue SCC, its primary role is in cases where surgery is not feasible or when there is incomplete tumor removal during surgery. In this case, RND is more appropriate as it addresses the regional lymph node involvement.

D. **Adjuvant chemotherapy (CT)** - Although CT is used in the management of oral tongue SCC, it is generally employed when the disease is advanced and radiation-resistant, or when surgery is difficult due to the tumor location. In this case, RND provides a more comprehensive treatment approach.

**Clinical Pearl:**

In cases of advanced oral tongue SCC, a comprehensive treatment plan includes a combination of surgery, radiotherapy, and/or chemotherapy, depending on the tumor stage and extent of disease. The choice of treatment depends on the patient's overall health condition, tumor size, and extent of lymph node involvement. In the given case, RND is the optimal treatment approach to address the regional lymph node involvement and ensure complete tumor removal, while considering the patient's age and potential complications from extensive surgery.