Infectious agent which is smaller than virus and having no protein coat is

Options

A. Virion
B. Viroids
C. Prions
D. Mycophages

Answer

To solve the question "Infectious agent which is smaller than virus and having no protein coat is," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for an infectious agent that is smaller than a virus and does not have a protein coat.

2. **Analyzing the Options**:
- **Option 1: Variants**: Variants refer to different forms of viruses. They are complete virus particles that consist of a protein coat (capsid) and nucleic acid (either DNA or RNA). Therefore, this option is incorrect.

- **Option 2: Viroids**: Viroids are indeed smaller than viruses and consist of a short strand of circular single-stranded RNA. They do not have a protein coat, making this option a potential correct answer.

- **Option 3: Prions**: Prions are infectious agents that are misfolded proteins. They do not contain any genetic material, but they are not smaller than viruses in terms of infectious agents. Thus, this option is incorrect.

- **Option 4: Mycophages**: Mycophages are viruses that infect fungi and, like other viruses, they have a protein coat. Therefore, this option is also incorrect.

3. **Conclusion**: After analyzing all the options, the only infectious agent that is smaller than a virus and lacks a protein coat is **Viroids**.

### Final Answer:
The correct answer is **Viroids**.

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