A virion is a

Options

A. Virus in stage of multiplication
B. Virus attached to host cell nucleus
C. Virus inside cytoplasm of host cell
D. Virus in cell free environment .

Answer

To answer the question "A virion is a", we will analyze the options provided and the definition of a virion.

### Step-by-Step Solution:

1. **Understanding the Term "Virion":**
- A virion is defined as a complete virus particle that consists of genetic material (either DNA or RNA) encased in a protein coat (capsid).

2. **Analyzing the Options:**
- **Option A:** Virus in a stage of multiplication.
- This option refers to the virus actively replicating within a host cell, which is not the definition of a virion.
- **Option B:** Virus attached to the host cell nucleus.
- This option describes a virus that is interacting with a host cell, which again does not define a virion.
- **Option C:** Virus inside the cytoplasm of the host cell.
- This option indicates that the virus is within a host cell, which does not fit the definition of a virion.
- **Option D:** Virus in a cell-free environment.
- This option correctly describes a virion, as it refers to the virus existing outside of a host cell, in a free state.

3. **Conclusion:**
- Based on the definitions and analysis of the options, the correct answer is **Option D: Virus in a cell-free environment**. This is because virions exist outside of host cells and are responsible for transferring the viral genome from one cell to another.

### Final Answer:
A virion is a virus in a cell-free environment.

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