Virion is

Options

A. nucleic acid of virus
B. antiviral agent
C. protein of virus
D. completely assembled virus outside host.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Term "Virion":**
- A virion is defined as a complete and fully developed viral particle. It is the infectious form of a virus that is capable of infecting a host.

2. **Composition of a Virion:**
- A virion consists of two main components:
- **Nucleic Acid:** This can be either DNA or RNA, which carries the genetic information of the virus.
- **Protein Coat (Capsid):** This is a protective layer that surrounds the nucleic acid. The capsid is made up of protein subunits called capsomers.

3. **Location of a Virion:**
- A virion exists outside of a host cell. It is the form of the virus that is capable of transmission from one host to another.

4. **Function of a Virion:**
- The primary role of a virion is to serve as a vehicle for transmitting the viral genetic material to new host cells, thereby facilitating infection.

5. **Identifying the Correct Option:**
- Based on the definition and characteristics of a virion, the correct answer to the question is: "completely assembled virus outside host."

**Final Answer:**
A virion is a completely assembled virus outside of a host, consisting of nucleic acid and a protein coat.

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