**Core Concept**
Hodgkin's Lymphoma (HL) is a type of cancer that originates from the lymphocytes, specifically the B cells, and is characterized by the presence of Reed-Sternberg cells. The Ann Arbor Staging System is used to classify the extent of disease spread in HL, which is crucial for determining treatment and prognosis.

**Why the Correct Answer is Right**
The patient's presentation of persistent fever, significant weight loss, and lymphadenopathy suggests widespread disease. The biopsy from the cervical nodes confirming Hodgkin's Lymphoma indicates the need to accurately stage the disease. According to the Ann Arbor Staging System, Stage II is defined by the presence of lymph node involvement on both sides of the diaphragm. In this case, the patient has cervical lymphadenopathy, which is on one side of the diaphragm, and axillary lymphadenopathy, which is on the other side of the diaphragm.

**Why Each Wrong Option is Incorrect**
**Option A:** Stage I would be incorrect as it involves a single lymph node group or a single extralymphatic organ or site.
**Option B:** Stage IV would be incorrect as it involves widespread disease, including at least one extralymphatic organ or site and/or bone marrow.
**Option C:** Stage III would be incorrect as it involves lymph node involvement on the same side of the diaphragm.

**Clinical Pearl / High-Yield Fact**
When staging Hodgkin's Lymphoma, it is essential to note that the presence of systemic symptoms such as fever, weight loss, and night sweats indicates a more advanced stage and a poorer prognosis.

**Correct Answer: C. Stage II involvement on both sides of the diaphragm.**