Select the odd one from the following .

Options

A. Anabaena
B. Nostoc
C. Oscillatoria
D. Rhizobium

Answer

To solve the question of selecting the odd one out from the given options, we will analyze each option based on their classification and characteristics.

### Step-by-Step Solution:

1. **Identify the Options:**
- Option 1: Anabena
- Option 2: Nostoc
- Option 3: Oscillatoria
- Option 4: Rhizobium

2. **Classify the First Three Options:**
- Anabena, Nostoc, and Oscillatoria are all classified as cyanobacteria, which are also known as blue-green algae. They are photosynthetic organisms that can produce their own food through photosynthesis and can also fix nitrogen.

3. **Analyze the Fourth Option:**
- Rhizobium, on the other hand, is a genus of bacteria that is not classified as cyanobacteria. It is primarily found in the root nodules of leguminous plants and plays a crucial role in nitrogen fixation, but it does not perform photosynthesis like the cyanobacteria.

4. **Conclusion:**
- Since Anabena, Nostoc, and Oscillatoria are all cyanobacteria and share similar characteristics, while Rhizobium is a distinct type of bacteria with different functions and characteristics, the odd one out is **Rhizobium**.

### Final Answer:
The odd one out is **Rhizobium**.

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