Which of the following is true about virus:

Options

A. Having well developed enzyme system
B. Having RNA or DNA as genetic material
C. These can be facultative parasite also
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding Viruses**: Begin by recognizing that viruses are unique entities that exhibit characteristics of both living and non-living things. They cannot carry out metabolic processes on their own and must rely on a host cell for replication and metabolism.

2. **Evaluating the Options**:
- **Option 1**: "Having well-developed enzyme system." This is incorrect because viruses do not possess their own metabolic machinery or enzyme systems. They rely on the host's cellular machinery to replicate and carry out metabolic functions.

- **Option 2**: "Having RNA or DNA as genetic material." This statement is true. Viruses contain either DNA or RNA as their genetic material, which can be single-stranded or double-stranded.

- **Option 3**: "These can be facultative parasites." This is incorrect. Viruses are classified as obligate parasites, meaning they must infect a host cell to reproduce and cannot survive independently.

3. **Conclusion**: After evaluating all the options, the only true statement about viruses is that they have RNA or DNA as genetic material. Therefore, the correct answer is **Option 2**.

---