Ctenophores are

Options

A. Exclusively marine
B. Exclusively fresh water
C. Both marine and fresh water
D. Both fresh water and terrestrial

Answer

**Step-by-Step Solution:**

1. **Identify the Organism**: The question is about Ctenophores, which are also known as comb jellies or sea walnuts.

2. **Habitat of Ctenophores**: Ctenophores are primarily found in marine environments. They are known to inhabit oceans and seas.

3. **Characteristics of Ctenophores**:
- They are **diploblastic**, meaning their body is composed of two layers: ectoderm and endoderm.
- They do not possess a mesoderm.
- They have a gelatinous body structure, which is typical for marine organisms.

4. **Reproductive Traits**: Ctenophores exhibit external fertilization, meaning that fertilization occurs outside their bodies. Their developmental process is indirect, involving a larval stage.

5. **Conclusion**: Based on the characteristics and habitat of Ctenophores, the correct answer to the question is that they are **exclusively marine** organisms.

**Final Answer**: Ctenophores are exclusively marine.

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