A: Nitrogen fixing bateria always live in symbiosis.
R; Symbiosis occurs between the organisms of the same species.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that "Nitrogen fixing bacteria always live in symbiosis."
- **Analysis**: Nitrogen-fixing bacteria, such as Rhizobium, can live in symbiotic relationships with leguminous plants, but they can also exist independently in the soil as free-living bacteria (e.g., Azotobacter, Nostoc). Therefore, the assertion is not entirely accurate.

2. **Understanding the Reason (R)**: The reason states that "Symbiosis occurs between the organisms of the same species."
- **Analysis**: Symbiosis refers to a close and often long-term interaction between two different biological species. For example, Rhizobium (a bacterium) and legumes (a plant) form a symbiotic relationship, indicating that symbiosis can occur between different species, not just the same species. Thus, this statement is also false.

3. **Conclusion**: Since both the assertion and the reason are false, we conclude that the correct answer is that both statements are incorrect.

### Final Answer:
Both the assertion (A) and the reason (R) are false.