True nucleus and mitochondria are absent in

Options

A. Cyanophyceae
B. Chlorophyceae
C. Myxomycetes
D. Azolla.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which organism lacks a true nucleus and mitochondria. This indicates that we are looking for a prokaryotic organism, as prokaryotes are characterized by the absence of a true nucleus and membrane-bound organelles.

2. **Identifying Prokaryotes vs. Eukaryotes**:
- Prokaryotes (e.g., bacteria) do not have a true nucleus and lack membrane-bound organelles such as mitochondria.
- Eukaryotes (e.g., plants, animals, fungi) have a true nucleus and possess membrane-bound organelles.

3. **Analyzing the Options**:
- **Cyanophyceae**: Also known as blue-green algae or cyanobacteria, these are prokaryotic organisms. Therefore, they lack a true nucleus and mitochondria.
- **Chlorophyceae**: This group refers to green algae, which are eukaryotic. They have a true nucleus and mitochondria.
- **Myxomycetes**: Known as slime molds, these are also eukaryotic organisms. They possess a true nucleus and mitochondria.
- **Azolla**: This is a type of fern that belongs to the kingdom Plantae, which is eukaryotic. It has a true nucleus and mitochondria.

4. **Conclusion**: Based on the analysis, the only option that lacks a true nucleus and mitochondria is **Cyanophyceae** (blue-green algae or cyanobacteria).

### Final Answer:
True nucleus and mitochondria are absent in **Cyanophyceae**.

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