All `N_(2)` fixers belong to

Options

A. Eubacteria
B. algae
C. plantae
D. protista

Explanation

**Step-by-Step Solution:**

1. **Understanding Nitrogen Fixation**: Nitrogen fixation is the process by which certain organisms convert atmospheric nitrogen (N₂) into ammonia (NH₃) or related compounds. This is crucial for the nitrogen cycle and for providing usable nitrogen to plants.

2. **Identifying Nitrogen Fixers**: The primary organisms that are known for nitrogen fixation are certain types of bacteria and cyanobacteria (also known as blue-green algae).

3. **Classification of Nitrogen Fixers**: These nitrogen-fixing organisms are classified under the domain of Eubacteria. Eubacteria are a large group of bacteria that are characterized by their prokaryotic cell structure.

4. **Kingdom Association**: Eubacteria, including nitrogen-fixing bacteria and cyanobacteria, belong to the kingdom Monera. This kingdom encompasses all prokaryotic organisms.

5. **Conclusion**: Therefore, the answer to the question is that all nitrogen fixers belong to Eubacteria.

**Final Answer**: All nitrogen fixers belong to Eubacteria.

---