**Core Concept**
Introns are non-coding regions of DNA or RNA that are removed during the process of RNA splicing. They are typically found in eukaryotic genes and are distinct from exons, which are the coding regions of a gene. The presence of introns allows for alternative splicing, enabling a single gene to encode multiple proteins.

**Why the Correct Answer is Right**
Introns are not found in prokaryotic DNA because prokaryotes lack the complex RNA splicing mechanisms present in eukaryotes. Prokaryotic genes are typically composed of a single, uninterrupted coding sequence, with no introns. This is because prokaryotes rely on a simpler form of transcription and translation, with minimal post-transcriptional processing.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because introns are a characteristic feature of eukaryotic DNA, not prokaryotic DNA.
* **Option B:** This option is incorrect because while some viruses may have introns, the presence of introns is not unique to viral DNA.
* **Option C:** This option is incorrect because while some eukaryotic genes may have a large number of introns, introns are not exclusively found in genes with many exons.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the presence of introns is a key characteristic that distinguishes eukaryotic from prokaryotic DNA, and understanding the mechanisms of RNA splicing is crucial for appreciating the complexities of gene expression in eukaryotic cells.

**Correct Answer:** D.