One of the special characters of coelenterata only is the occurrence of

Options

A. Hermaphroditism
B. Flame cells
C. Polymorphism
D. Nematocysts

Explanation

### Step-by-Step Solution

1. **Understanding Coelenterata**: Coelenterata, also known as Cnidaria, is a phylum that includes organisms like jellyfish, corals, and sea anemones. They are characterized by their unique body structure and specialized cells.

2. **Identifying Special Characteristics**: To determine the special characteristics of Coelenterata, we need to evaluate various features that may be exclusive to this phylum.

3. **Evaluating Hermaphroditism**: Hermaphroditism, where an organism has both male and female reproductive organs, is not unique to Coelenterata. It is found in various other organisms across different phyla. Thus, it cannot be considered a special characteristic of Coelenterata.

4. **Considering Flame Cells**: Flame cells are specialized excretory cells found in Platyhelminthes (flatworms) and are not present in Coelenterata. Therefore, flame cells are also not a special characteristic of this phylum.

5. **Assessing Polymorphism**: Polymorphism refers to the occurrence of different forms or stages in the life cycle of an organism. While Coelenterata may exhibit some forms of polymorphism, this characteristic is also found in other phyla, such as Arthropoda. Hence, it is not exclusive to Coelenterata.

6. **Identifying Nematocysts**: Nematocysts are specialized cells unique to Coelenterata. These cells contain stinging structures that are used for capturing prey and defense. Since nematocysts are not found in other phyla, they are indeed a special characteristic of Coelenterata.

7. **Conclusion**: The special character of Coelenterata that is unique to this phylum is the occurrence of nematocysts.

### Final Answer
One of the special characters of Coelenterata only is the occurrence of **nematocysts**.

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