Assertion: Each stoma is composed of two bean shaped cells known as guard cells.
Reason: Guard cells regulate the opening and closing of stomata.

Options

A. If both assertion and reason are true and reason is the correct explanantion of assertion
B. if both assertion and reason are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false.
D. if both assertion and reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Each stoma is composed of two bean-shaped cells known as guard cells."
- **Explanation**: Stomata are small openings found on the surface of leaves, primarily on the epidermis. Each stoma is indeed formed by a pair of specialized cells called guard cells, which are typically bean-shaped.

2. **Understanding the Reason**: The reason states that "Guard cells regulate the opening and closing of stomata."
- **Explanation**: Guard cells control the size of the stomatal pore. When guard cells take up water and swell, they curve away from each other, causing the stomatal pore to open. Conversely, when they lose water, they become flaccid and the pore closes. This regulation is crucial for gas exchange and transpiration.

3. **Evaluating the Relationship**: Now, we need to evaluate whether the reason correctly explains the assertion.
- **Analysis**: While both the assertion and reason are true statements, the reason does not provide a direct explanation for the assertion. The assertion describes the structure of the stoma, while the reason describes the function of the guard cells.

4. **Conclusion**: Since both the assertion and reason are true, but the reason does not explain the assertion, we conclude that:
- **Final Answer**: Both the assertion and reason are true, but the reason is not the correct explanation for the assertion.