## Core Concept
Viroids are infectious agents composed entirely of **RNA**, without a protein coat. They are known to infect plants and cause various diseases. The core concept here revolves around the unique characteristics of viroids, particularly their composition and the nature of their genetic material.

## Why the Correct Answer is Right
The correct answer, , highlights that viroids are made up of single-stranded **RNA**. This RNA is not enclosed within a protein coat, which distinguishes viroids from viruses. The genetic material of viroids is **circular single-stranded RNA**, and they replicate in the host plant cells, often interfering with the host's metabolic processes.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because viroids do not have a **protein coat**; they consist solely of RNA.
- **Option B:** This option is incorrect as it does not accurately describe viroids; viroids are indeed **RNA** but specifying "double-stranded" is incorrect.
- **Option C:** This option might seem plausible but is incorrect because viroids are **not DNA**; they are RNA.

## Clinical Pearl / High-Yield Fact
A key point to remember is that viroids are **exclusively found in plants** and are known to cause significant economic losses in agriculture. Unlike viruses, viroids do not encode for proteins; their pathogenicity is thought to be related to the **RNA** itself, possibly through interfering with host gene expression.

## Correct Answer Line
**Correct Answer: .**