Perisarc is absent in Hydra because

Options

A. It is fixed
B. It is free swimming
C. Epidermis cannot secrete it
D. None of the above.

Answer

### Step-by-Step Solution:

1. **Understanding Perisarc**:
- Perisarc is a protective outer covering made of chitin that is found in certain colonial organisms within the phylum Cnidaria. It serves to protect and provide flexibility to the colonies.

2. **Characteristics of Hydra**:
- Hydra is a freshwater organism that is classified under the phylum Cnidaria. Unlike many other cnidarians, Hydra is not colonial; it exists as a solitary organism.

3. **Colonial vs. Solitary Organisms**:
- In colonial organisms, the perisarc is important for protecting the entire colony. However, since Hydra does not form colonies, the need for a perisarc is diminished.

4. **Hydra's Lifestyle**:
- Hydra is primarily a sedentary organism, meaning it is generally fixed in one place and does not swim freely like some other cnidarians. However, the phrasing of the question suggests that the absence of perisarc is related to its lifestyle.

5. **Analyzing the Options**:
- The options provided are:
- It is fixed
- It is free swimming
- Epidermis cannot secrete it
- None of the above
- Since Hydra does not form colonies and is not free swimming in the same sense as other cnidarians, the correct answer is that it is free swimming.

6. **Conclusion**:
- Therefore, the absence of perisarc in Hydra is due to its nature as a solitary organism rather than a colonial one, leading to the conclusion that the correct answer is "it is free swimming."