What is/are true about viruses?

Options

A. They can be crystallised and stored for several years.
B. They occur as parasites in living cells.
C. They are devoid of genetic material of their own.
D. Their protein coat is known as capsid.

Answer

### Step-by-Step Solution:

1. **Understanding Viruses**: Viruses are unique entities that require a host cell to replicate and survive. They are not classified as living organisms when outside a host.

2. **Analyzing the Options**:
- **Option 1**: "They can be crystallized and stored for several years."
- This statement is true. Viruses can be crystallized, which allows them to be stored for extended periods. The first crystallization of a virus was achieved with the Tobacco Mosaic Virus (TMV) in 1935.

- **Option 2**: "They occur as parasites in living cells."
- This statement is also true. Viruses are obligate parasites, meaning they cannot reproduce or carry out metabolic processes without a host cell. They are considered "alive" only within a host.

- **Option 3**: "They are devoid of genetic material of their own."
- This statement is false. Viruses possess genetic material, which can be either DNA or RNA, and they require this genetic material to infect host cells and replicate.

- **Option 4**: "Their protein coat is known as capsid."
- This statement is true. The protein coat that surrounds the viral nucleic acid is called the capsid, which serves to protect the genetic material and assist in the infection of host cells.

3. **Conclusion**: Based on the analysis, the true statements about viruses are:
- Option 1: True
- Option 2: True
- Option 4: True
- Option 3: False

Thus, the correct answers are Options 1, 2, and 4.