True nucleus is absent in

Options

A. Mucor
B. Vaucheria
C. Volvox
D. Anabaena

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which organism lacks a true nucleus. A true nucleus is a characteristic of eukaryotic cells, while prokaryotic cells do not have a true nucleus.

2. **Identifying Prokaryotes and Eukaryotes**:
- Prokaryotes are organisms that do not have a true nucleus or membrane-bound organelles. They belong to the Kingdom Monera, which includes bacteria and cyanobacteria.
- Eukaryotes, on the other hand, have a true nucleus and membrane-bound organelles. They belong to various kingdoms, including Fungi and Plantae.

3. **Analyzing the Options**:
- **Mucor**: This is a fungus that belongs to the phylum Zygomycota and is part of the Kingdom Fungi. Since it is a eukaryote, it has a true nucleus.
- **Vichyria**: This is a yellow-green alga that belongs to the Kingdom Plantae. It is also a eukaryote, thus it has a true nucleus.
- **Volvox**: This is a green alga that belongs to the family Volvaceae and is part of the Kingdom Plantae. It is a eukaryote and has a true nucleus.
- **Anabina**: This is a blue-green alga, also known as cyanobacteria, and belongs to the Kingdom Monera. It is a prokaryote and lacks a true nucleus.

4. **Conclusion**: Among the given options, Anabina is the only organism that is a prokaryote and therefore lacks a true nucleus.

5. **Final Answer**: The correct answer is **Anabina**.

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