**Core Concept**
Hodgkin's lymphoma is a type of cancer that affects the immune system, specifically the lymphatic system. It is characterized by the presence of abnormal lymphocytes called Reed-Sternberg cells, which are a hallmark of this disease.

**Why the Correct Answer is Right**
Hodgkin's lymphoma is primarily caused by a viral infection, specifically the Epstein-Barr virus (EBV). EBV is a member of the herpesvirus family and is known to cause infectious mononucleosis, also known as glandular fever. In some cases, EBV can integrate into the host genome and lead to the development of Hodgkin's lymphoma. The exact mechanism is not fully understood, but it is believed that EBV can dysregulate the host's immune system, leading to the uncontrolled growth of Reed-Sternberg cells.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while genetic mutations can contribute to the development of lymphoma, they are not the primary cause of Hodgkin's lymphoma.
* **Option B:** This option is incorrect because while radiation exposure can increase the risk of lymphoma, it is not a direct cause of Hodgkin's lymphoma.
* **Option C:** This option is incorrect because while certain viral infections can increase the risk of lymphoma, they are not the primary cause of Hodgkin's lymphoma.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that EBV is a common cause of infectious mononucleosis, and patients with this condition should be closely monitored for signs and symptoms of Hodgkin's lymphoma.

**Correct Answer: D. Epstein-Barr virus**