Monerans comprise

Options

A. Bacteria
B. Nitrogen fixing organisms
C. Cyanophyceae
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Monerans**: Monerans refer to organisms that belong to the kingdom Monera, which includes all prokaryotic organisms. Prokaryotes are characterized by the absence of a true nucleus and membrane-bound organelles.

2. **Characteristics of Prokaryotes**: Prokaryotic cells lack a defined nucleus; instead, their genetic material is suspended in the cytoplasm. They also do not have membrane-bound organelles such as mitochondria, chloroplasts, or the endoplasmic reticulum.

3. **Components of Kingdom Monera**:
- **Eubacteria**: This group includes all true bacteria, which are the most common prokaryotes.
- **Cyanobacteria**: Also known as blue-green algae, these organisms are photosynthetic and can fix nitrogen.
- **Archaebacteria**: These are ancient prokaryotes that often live in extreme environments.

4. **Nitrogen-Fixing Organisms**: Many nitrogen-fixing organisms, such as Rhizobium, Nostoc, and Anabaena, fall under the categories of either eubacteria or cyanobacteria. Therefore, they are also part of the kingdom Monera.

5. **Conclusion**: Since Monerans include bacteria, nitrogen-fixing organisms, and cyanobacteria, the correct answer to the question "Monerans comprise" is **D. All of the above**.

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