Bacteria Azotobacter and Clostridium drive the ...... cycle.

Options

A. carbon
B. nitrogen
C. oxygen
D. energy

Explanation

**Step-by-Step Text Solution:**

1. **Identify the Bacteria**: The question mentions two specific bacteria: Azotobacter and Clostridium.

2. **Understand Their Role**: Both Azotobacter and Clostridium are known as nitrogen-fixing bacteria. This means they have the ability to convert atmospheric nitrogen (N₂) into a form that can be used by living organisms, particularly plants.

3. **Define Nitrogen Fixation**: Nitrogen fixation is the process through which nitrogen in the atmosphere is converted into ammonia (NH₃) or related compounds in soil. This is crucial because most living organisms cannot utilize atmospheric nitrogen directly.

4. **Differentiate Types of Nitrogen-Fixing Bacteria**: There are two main types of nitrogen-fixing bacteria:
- **Symbiotic Bacteria**: These bacteria, like Rhizobium, form a symbiotic relationship with certain plants (like legumes).
- **Free-Living Bacteria**: Azotobacter and Clostridium fall into this category. They do not require a host plant and can fix nitrogen independently.

5. **Relate to the Nitrogen Cycle**: The process of nitrogen fixation by these bacteria is a key step in the nitrogen cycle, which is the series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms.

6. **Conclude the Answer**: Therefore, the correct answer to the question is that Azotobacter and Clostridium drive the **Nitrogen Cycle**.

**Final Answer**: Azotobacter and Clostridium drive the Nitrogen Cycle.

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