Assertion: Bryophytes are not a successul land plants.
Reason: In bryophytes there is lack of vascular system.

Options

A. If both assertion and Reason are true and the reason is a correct explanation of the assertion.
B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion and Reason are False.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Bryophytes are not successful land plants." To evaluate this, we need to consider what is meant by "successful" in the context of land plants. Successful land plants are typically those that can thrive in a variety of terrestrial environments and have adaptations that allow them to reproduce and grow efficiently on land.

2. **Understanding the Reason**: The reason given is that "In bryophytes there is a lack of vascular system." Vascular systems in plants consist of specialized tissues (xylem and phloem) that transport water, nutrients, and food throughout the plant. The absence of a vascular system in bryophytes limits their ability to transport water and nutrients effectively.

3. **Connecting Assertion and Reason**: The assertion claims that bryophytes are not successful land plants, and the reason provided explains this by pointing out their lack of a vascular system. This lack indeed affects their ability to thrive in terrestrial environments, as they rely on water for reproduction and cannot efficiently transport nutrients and water over long distances.

4. **Evaluating the Truth of Assertion and Reason**:
- The assertion is true because bryophytes are limited in their ability to occupy diverse terrestrial habitats compared to vascular plants.
- The reason is also true because the absence of a vascular system is a significant factor that contributes to their limited success as land plants.

5. **Conclusion**: Since both the assertion and the reason are true, and the reason correctly explains the assertion, we can conclude that the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.