Which is absent in viruses?

Options

A. Nucleic acid
B. Protoplasm
C. Protein
D. a and c

Answer

To determine what is absent in viruses, we can analyze the options provided:

1. **Nucleic Acid**: Viruses contain nucleic acids, which can be either RNA or DNA. This is essential for their replication and genetic information.

2. **Protoplasm**: Viruses do not have protoplasm. Protoplasm is the living substance within a cell, and since viruses are acellular (not made of cells), they lack this component.

3. **Protein**: Viruses do have proteins, specifically in the form of a protective coat called the capsid that surrounds their nucleic acid.

4. **A and C**: This option suggests that both nucleic acid and protein are absent, which is incorrect since viruses contain both.

From this analysis, we can conclude that the component that is absent in viruses is **protoplasm**.

### Final Answer:
**Protoplasm is absent in viruses.**