Characteristic feature of coelenterata is

Options

A. All are marine
B. Presence of tentacles around mouth
C. Polyp
D. Gastrovascular cavity.

Answer

**Step-by-Step Solution:**

1. **Understanding Coelenterata**: Coelenterata, also known as Cnidaria, includes organisms such as jellyfish, corals, and sea anemones. They are primarily aquatic and exhibit certain key features.

2. **Identifying Characteristic Features**: The question asks for a characteristic feature of Coelenterata. We need to evaluate the options provided to determine which one is unique to this phylum.

3. **Evaluating the Options**:
- **Option 1: All are marine**: While it is true that most Coelenterates are marine, this is not a unique characteristic as other organisms can also be marine.
- **Option 2: Presence of tentacles around the mouth**: Many organisms, including those from other phyla, have tentacles, so this is not a distinguishing feature.
- **Option 3: Polyp**: The polyp form is present in several other phyla, not just Coelenterata, making this option incorrect as well.
- **Option 4: Gastrovascular cavity**: This is a significant feature of Coelenterata. It serves as a primary organ for digestion and circulation, having a single opening for both food intake and waste excretion.

4. **Conclusion**: After evaluating all options, the correct answer is the presence of a gastrovascular cavity, as it is a defining characteristic of Coelenterata.

**Final Answer**: The characteristic feature of Coelenterata is the presence of a gastrovascular cavity.

---