Assertion : All bryophytes are called as amphibians of plant kingdom.
Reason : Water is necessary to complete their life-cycle.

Options

A. If both assertion and reason are true and reason is the correct explanation 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.

Explanation

### Step-by-Step Solution:

1. **Understand the Assertion**: The assertion states that "All bryophytes are called amphibians of the plant kingdom." This means that bryophytes have characteristics that allow them to thrive in both terrestrial (land) and aquatic (water) environments.

2. **Understand the Reason**: The reason provided is that "Water is necessary to complete their life-cycle." This indicates that bryophytes require water for reproduction and other life processes.

3. **Analyze the Relationship**: To determine if the reason supports the assertion, we need to see if the necessity of water for the life cycle of bryophytes justifies their classification as amphibians.

4. **Evaluate the Characteristics of Bryophytes**: Bryophytes, which include mosses and liverworts, are indeed found in moist environments and require water for fertilization. They can survive on land but depend on water for certain stages of their life cycle, such as sperm motility for fertilization.

5. **Conclusion**: Since both the assertion and the reason are true, and the reason explains why bryophytes are called amphibians (due to their dependence on water), we conclude that the assertion is correct and the reason is a valid explanation.

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