Select the mismatch:

Options

A. Frankia- Alnus
B. Rhodosphirillum- Mycorrhiza
C. Anabaena- Nitrogen fixer
D. Rhizobium - Alfalfa

Answer

To solve the question "Select the mismatch," we will analyze each option provided in the question step by step.

### Step 1: Analyze Option 1
- **Francia and Alnus**: Francia is a type of bacteria that forms a symbiotic relationship with non-leguminous plants. Alnus is a genus of trees that is indeed associated with Francia.
- **Conclusion**: This option is correct.

**Hint**: Check if the organisms mentioned in the option have a known symbiotic relationship.

### Step 2: Analyze Option 2
- **Rhodospirillum and Mycorrhiza**: Rhodospirillum is a type of bacteria that can be autotrophic or chemo-autotrophic. Mycorrhiza, on the other hand, refers to a symbiotic association between fungi and the roots of higher plants. These two do not have a direct association.
- **Conclusion**: This option is mismatched.

**Hint**: Identify if the organisms in the option are from the same category or have a known interaction.

### Step 3: Analyze Option 3
- **Anabena and Nitrogen Fixer**: Anabena is a genus of blue-green algae (cyanobacteria) known for its ability to fix nitrogen. It is a free-living nitrogen fixer.
- **Conclusion**: This option is correct.

**Hint**: Look for organisms that are known for specific functions like nitrogen fixation.

### Step 4: Analyze Option 4
- **Rhizobium and Alfalfa**: Rhizobium is a genus of bacteria that forms symbiotic relationships with leguminous plants, including alfalfa.
- **Conclusion**: This option is correct.

**Hint**: Verify if the bacteria mentioned are known to associate with the specified plant type.

### Final Conclusion
After analyzing all the options, we find that the mismatch is in **Option 2: Rhodospirillum and Mycorrhiza**.

### Answer
The mismatch is **Option 2: Rhodospirillum and Mycorrhiza**.