Assertion : Sponges exhibit cellular level of organisation.
Reason: In sponges, cells are arranged as loose cell aggregates.

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. **Understanding the Assertion**: The assertion states that "Sponges exhibit cellular level of organization." This means that sponges, which belong to the phylum Porifera, have a basic form of organization where their cells are not organized into true tissues or organs, but rather function as individual units.

2. **Understanding the Reason**: The reason provided is "In sponges, cells are arranged as loose cell aggregates." This indicates that the cells in sponges are not tightly bound together like in more complex organisms, but are instead grouped together in a way that allows them to function independently while still being part of the sponge.

3. **Evaluating the Truth of the Statements**:
- The assertion is true because sponges do indeed exhibit a cellular level of organization.
- The reason is also true because sponges consist of loosely aggregated cells, which is characteristic of their structure.

4. **Determining the Relationship**: Since both the assertion and the reason are true, we need to determine if the reason correctly explains the assertion. The reason does explain why sponges have a cellular level of organization, as the loose arrangement of cells is what defines this level of organization.

5. **Conclusion**: Both the assertion and the reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct answer is that both statements are true and the reason is the correct explanation of the assertion.

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

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