## **Core Concept**
The question tests knowledge of oncogenic viruses, specifically RNA viruses that can cause cancer. Oncogenic viruses are viruses that have the potential to cause cancer. They can lead to tumor formation through various mechanisms, including integration into the host genome and disrupting normal cellular functions.

## **Why the Correct Answer is Right**
The correct answer, **Human T-Lymphotropic Virus-1 (HTLV-1)**, is indeed an oncogenic RNA virus. HTLV-1 is a retrovirus that integrates into the host genome and can lead to adult T-cell leukemia/lymphoma (ATL). It does so by promoting proliferation of infected T-cells and disrupting normal cellular regulation. HTLV-1 is known to be endemic in certain regions and is associated with a high risk of ATL.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain strains of the Hepatitis C virus (HCV) are associated with hepatocellular carcinoma, HCV is a DNA virus, not an RNA virus, making it incorrect for this question.
- **Option B:** Human Papillomavirus (HPV) is a DNA virus known to cause cervical cancer, among others. It is not an RNA virus.
- **Option D:** Epstein-Barr Virus (EBV) is a DNA virus associated with several cancers, including Burkitt's lymphoma and nasopharyngeal carcinoma. It is not an RNA virus.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while many viruses can cause cancer, the question specifically asks for an RNA virus. HTLV-1 is a significant example because it directly causes cancer through its integration and alteration of host cell genetics.

## **Correct Answer:** C. HTLV-1.