Nitrogenase enzyme is produced by:

Options

A. All prokaryotes
B. Some eukaryotes
C. All eukaryotes
D. Some prokaryotes

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogenase**: Nitrogenase is an enzyme that plays a crucial role in the process of nitrogen fixation, which is the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) that plants can utilize.

2. **Identifying Organisms that Produce Nitrogenase**:
- Nitrogenase is primarily found in certain microorganisms.
- It is produced by some prokaryotes, particularly certain bacteria, including those that form symbiotic relationships with leguminous plants (like Rhizobium).

3. **Role of Eukaryotes**:
- While some eukaryotic organisms, such as certain fungi and plants, may benefit from nitrogen-fixing bacteria, they do not produce nitrogenase themselves.
- Eukaryotes generally lack the ability to fix nitrogen because they do not synthesize this enzyme.

4. **Conclusion**: Based on the information, nitrogenase is produced by some prokaryotes (specifically certain bacteria) and not by all prokaryotes or eukaryotes.

5. **Final Answer**: The correct answer is **some prokaryotes**.