**Core Concept**
The question is testing the student's knowledge of the classification of viruses based on their genetic material. RNA viruses are a large group of viruses that use RNA as their genetic material, replicating through an RNA intermediate.

**Why the Correct Answer is Right**
RNA viruses are a diverse group that includes several important pathogens, such as influenza, HIV, and hepatitis C. They replicate through an RNA intermediate and often have a high mutation rate due to the lack of proofreading during RNA replication. This high mutation rate allows RNA viruses to rapidly evolve and adapt to changing environments.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because DNA viruses use DNA as their genetic material, replicating through a DNA intermediate.
* **Option B:** This option is incorrect because prions are infectious proteins that do not contain genetic material.
* **Option C:** This option is incorrect because viroids are small, single-stranded RNA molecules that do not encode proteins, but are not considered viruses.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that RNA viruses are more prone to mutation and can rapidly evolve, making them challenging to treat with antiviral medications.

**Correct Answer: C. Influenza**