The viruses are non-cellular organisms that are characterised by-

Options

A. Having no nucleic acid
B. Having an active structure outside the living cell
C. Having an inert crystalline structure outside the cell
D. Their hyperactivity outside the cell

Answer

### Step-by-Step Solution:

1. **Understanding Viruses**: Viruses are classified as non-cellular organisms, meaning they do not have a cellular structure like living organisms such as plants and animals.

2. **Characteristics of Viruses**:
- **Nucleoprotein Composition**: Viruses are made up of nucleic acid (either DNA or RNA) and a protein coat called a capsid. This means they do contain nucleic acid, which is essential for their replication and function.
- **Inactivity Outside Host Cells**: Viruses are inactive outside of a living cell. They do not carry out metabolic processes on their own and cannot reproduce without a host cell.
- **Crystalline Structure**: When isolated, viruses can exhibit a crystalline structure, which is a characteristic of their inert state outside of a host.

3. **Evaluating Options**:
- **Option 1**: "Having non-nucleic acid" - This is incorrect because viruses do contain nucleic acids.
- **Option 2**: "Having an active structure outside the living cell" - This is incorrect since viruses are inactive outside of host cells.
- **Option 3**: "Having an inert crystalline structure outside the cell" - This is correct as viruses can form crystalline structures when not in a host.

4. **Conclusion**: The correct characteristic of viruses is that they have an inert crystalline structure outside the living cell, confirming that they are non-cellular organisms.

### Final Answer:
Viruses are non-cellular organisms characterized by having an inert crystalline structure outside the living cell.

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