Assertion :- Coelenterates have tissue grade of organisation.
Reason :- In coelenterates the cells performing the same function are arranged into group.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & 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 & Reason are false.

Answer

To solve the question, we need to analyze the assertion and reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Coelenterates have tissue grade of organization."
- Coelenterates, also known as Cnidarians, include organisms like jellyfish, corals, and sea anemones. They are indeed multicellular organisms that exhibit a tissue level of organization.

2. **Understanding the Reason**:
- The reason provided is "In coelenterates, the cells performing the same function are arranged into groups."
- This statement is true because in coelenterates, cells that perform similar functions do indeed group together to form tissues. This is a characteristic feature of organisms with a tissue grade of organization.

3. **Evaluating the Relationship**:
- Since both the assertion and the reason are true, we need to determine if the reason correctly explains the assertion.
- The reason explains why coelenterates have a tissue grade of organization, as it describes how their cells are organized into functional groups.

4. **Conclusion**:
- Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
- The correct answer is **Option 1**: Both assertion and reason are true, and the reason is the correct explanation of the assertion.