Which of these do not have a regular cell structure ?

Options

A. Bacteria
B. Viruses
C. Protozoa
D. Algae

Explanation

### Step-by-Step Solution:

1. **Understanding Cell Structure**: Begin by recognizing that living organisms are made up of cells, which typically have a regular structure. This includes components like the nucleus, cytoplasm, and various organelles (e.g., mitochondria, Golgi apparatus).

2. **Identifying Organisms**: The question asks which organisms do not have a regular cell structure. Common categories of organisms include bacteria, protozoa, algae, and viruses.

3. **Analyzing Viruses**: Viruses are unique in that they do not exhibit a typical cellular structure. They consist of a protein coat (capsid) that protects their genetic material (DNA or RNA). Unlike other living organisms, they lack cellular machinery and organelles.

4. **Comparing with Other Organisms**: In contrast, bacteria, protozoa, and algae possess a regular cell structure with various organelles. They can carry out metabolic processes independently.

5. **Conclusion**: Based on the analysis, the organism that does not have a regular cell structure is the virus. Viruses are classified as non-living entities when outside a host, as they cannot replicate or perform metabolic functions without a host cell.

### Final Answer:
Viruses do not have a regular cell structure.

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