An exclusively marine phylum is

Options

A. Mollusca
B. Coelenterata
C. Sponges
D. Echinodermata

Answer

To answer the question "An exclusively marine phylum is," we can follow these steps:

### Step 1: Understand the Question
The question is asking for a phylum that consists entirely of marine organisms. This means we need to identify a group of animals that only live in saltwater environments.

**Hint:** Think about the characteristics of different animal phyla and their habitats.

### Step 2: Identify Marine Phyla
Several animal phyla exist, and many of them include both marine and freshwater species. We need to focus on those that are exclusively marine.

**Hint:** Consider the well-known phyla and their typical environments.

### Step 3: Consider Echinodermata
One of the phyla that is known to be exclusively marine is Echinodermata. Members of this phylum include sea stars, sea urchins, and sea cucumbers, all of which live in marine environments.

**Hint:** Recall examples of organisms that belong to the Echinodermata phylum.

### Step 4: Confirm Characteristics
Echinoderms exhibit unique characteristics such as radial symmetry and a water vascular system, which are adaptations to their marine lifestyle. They are not found in freshwater or terrestrial environments.

**Hint:** Think about the defining features of Echinodermata that support their marine existence.

### Step 5: Conclusion
Based on the information gathered, we can confidently conclude that the answer to the question is Echinodermata, as it is the only phylum that is exclusively marine.

**Final Answer:** The exclusively marine phylum is Echinodermata.

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