Assertion: Dicot roots are mostly tetrach.
Reason: There occur four phloem bundles forming rays.

Options

A. If both Assertin and Reason are true and the Reason is the correct explanatin of the Assertion.
B. If both Assertion and Reason are true, but the Reason is not the correct explanation of the Assertion.
C. If Assertion is true, Reason is false.
D. If both Assertion and Reason 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 "Dicot roots are mostly tetrach."
- In botanical terms, "tetrach" refers to having four vascular bundles. However, dicot roots can have a variety of arrangements, including diarch (two bundles), triarch (three bundles), and polyarch (more than four bundles). Therefore, stating that dicot roots are "mostly tetrach" is misleading and incorrect.

2. **Understanding the Reason**:
- The reason provided states that "There occur four phloem bundles forming rays."
- This statement is also incorrect because while some plants may have multiple phloem bundles, it is not a defining characteristic of all dicot roots. The arrangement of vascular bundles can vary widely among different species of dicots.

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

### Final Answer:
Both the assertion and the reason are false.