Viroids have

Options

A. Single stranded RNA not enclosed by protein coat
B. Single stranded DNA not enclosed by protein coat
C. Double stranded DNA enclosed by protein coat
D. Double stranded RNA enclosed by protein coat

Explanation

**Step-by-Step Solution:**

1. **Understanding Viroids**: Viroids are small infectious agents that are distinct from viruses. They are known to cause diseases primarily in plants.

2. **Identifying the Genetic Material**: The genetic material of viroids is composed of RNA. Specifically, viroids contain single-stranded RNA (ssRNA).

3. **Presence of Protein Coat**: Unlike viruses, viroids do not have a protein coat (capsid) surrounding their RNA. This is a key characteristic that differentiates them from viruses.

4. **Analyzing the Options**:
- **Option A**: Single-stranded RNA not enclosed by a protein coat. This is correct.
- **Option B**: Single-stranded DNA not enclosed by a protein coat. This is incorrect because viroids do not contain DNA.
- **Option C**: Double-stranded DNA enclosed by a protein coat. This is incorrect as viroids do not have DNA and also lack a protein coat.
- **Option D**: Double-stranded RNA enclosed by a protein coat. This is incorrect for the same reasons as above.

5. **Conclusion**: Based on the characteristics of viroids, the correct answer is **Option A: single-stranded RNA not enclosed by a protein coat**.

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