Assertion : In cycas, nitrogen fixation is found
Reason : In coralloid roots of cycas, cyanobacteria present

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but Ris not correct explanation of A
C. A is true but R is false
D. A and R are false

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "In Cycas, nitrogen fixation is found."
- This means that Cycas, a genus of cycads, has the ability to fix atmospheric nitrogen, which is essential for the growth of plants.

2. **Understanding the Reason**:
- The reason states that "In coralloid roots of Cycas, cyanobacteria are present."
- Coralloid roots are specialized structures in Cycas that house cyanobacteria, which are known for their ability to fix nitrogen.

3. **Linking Assertion and Reason**:
- The presence of cyanobacteria in the coralloid roots of Cycas is directly related to the nitrogen-fixing capability of the plant.
- Cyanobacteria convert atmospheric nitrogen into a form that plants can use, thus supporting the assertion.

4. **Evaluating Truthfulness**:
- Both the assertion and the reason are true.
- The reason correctly explains why nitrogen fixation occurs in Cycas.

5. **Conclusion**:
- Since both the assertion and the reason are true, and the reason is the correct explanation of the assertion, the answer is option A: Both assertion and reason are true, and the reason is the correct explanation of the assertion.