**Core Concept**
The TNM staging system is a widely used classification system for cancer staging, which takes into account the size and extent of the primary tumor (T), the involvement of lymph nodes (N), and the presence or absence of metastasis (M). In the context of oral cancer, the TNM staging system is essential for determining the prognosis and guiding treatment decisions.

**Why the Correct Answer is Right**
The presence of a single ipsilateral lymph node measuring 2 cm with capsular spread indicates lymph node metastasis. According to the TNM staging system, a lymph node is considered to be involved if it meets certain criteria, including a minimum size of 3 cm or more, or if it has capsular or extranodal spread. Since the lymph node in this case measures 2 cm and has capsular spread, it would be categorized as N1. However, given the presence of capsular spread, it would be more accurately classified as N1c, but since N1c is not an option given, we will consider the closest option available.

**Why Each Wrong Option is Incorrect**
**Option A:** Not provided
**Option B:** Not provided
**Option C:** Not provided
**Option D:** Not provided

**Clinical Pearl / High-Yield Fact**
When evaluating lymph nodes for metastasis, it's essential to assess not only the size but also the presence of capsular or extranodal spread, as these features can significantly impact the staging and prognosis of the disease.

**Correct Answer: C.**