Assertion :- Endosperm increases the success rate of seedling development.
Reason :- Endosperm arises from PEC.

Options

A. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion
B. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
C. Assertion is true but the Reason is false
D. Both the statements are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Endosperm increases the success rate of seedling development." This is true as endosperm provides essential nutrients to the developing embryo, which is critical for successful germination and seedling growth.

2. **Role of Endosperm**: The endosperm serves multiple functions:
- It nourishes the growing embryo by supplying necessary nutrients.
- It protects the embryo during development and germination.
- It acts as a mechanical barrier, controlling the growth of the embryo.

3. **Understanding the Reason**: The reason given is "Endosperm arises from PEC." PEC stands for Primary Endosperm Cell, which is formed through a process known as triple fusion.

4. **Triple Fusion Process**: In angiosperms, triple fusion occurs when one male gamete fuses with two polar nuclei in the embryo sac. This fusion results in the formation of the Primary Endosperm Cell, which is triploid (3n).

5. **Formation of Endosperm**: The Primary Endosperm Cell undergoes repeated divisions to form the triploid endosperm tissue. This tissue is crucial for providing nutrition to the developing embryo.

6. **Conclusion**: Both the assertion and reason are true statements. However, the reason provided does not directly explain why the assertion is true. The assertion focuses on the role of endosperm in seedling development, while the reason explains how endosperm is formed.

### Final Statement:
- The assertion is true, and the reason is also true, but the reason is not the correct explanation for the assertion.