**Core Concept**
The question tests the understanding of viral genomes, specifically the type of nucleic acid present in different virus families. **Genome structure** is a crucial aspect of virology, as it determines the classification, replication, and characteristics of viruses. Viruses can have either **DNA or RNA** as their genetic material, and it can be single-stranded or double-stranded.

**Why the Correct Answer is Right**
The correct answer is related to the fact that some viruses have a **double-stranded RNA (dsRNA)** genome. **Reoviruses** are known to have a **dsRNA** genome, which is a distinctive characteristic of this virus family. This genome structure is important for the virus's replication and transcription processes.

**Why Each Wrong Option is Incorrect**
**Option A:** Orthomyxoviruses have a single-stranded RNA genome. **Option B:** Poxviruses have a double-stranded DNA genome. **Option C:** Parvoviruses have a single-stranded DNA genome.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the type of genetic material and its structure can significantly influence the virus's behavior, replication, and interaction with the host cell. Knowing the genome type can help in understanding the virus's replication strategy and developing antiviral therapies.

**Correct Answer:** D. Reoviruses