Hydra contracts its body by means of

Options

A. Interstitial cells
B. Cnidoblasts
C. Nutritive cells
D. Epithelio-muscular cells.

Answer

To answer the question "Hydra contracts its body by means of," we need to analyze the options provided and understand the role of different cell types in Hydra.

### Step-by-Step Solution:

1. **Understand Hydra's Body Structure**: Hydra is a simple organism belonging to the phylum Cnidaria. It has a body structure that includes various types of cells, each with specific functions.

2. **Identify the Cell Types**: The options provided include interstitial cells, nematoblast cells, nutritive cells, and epithelial muscle cells. We need to evaluate each of these in the context of body contraction.

3. **Evaluate Interstitial Cells**: Interstitial cells are responsible for forming nerve cells and nematoblasts (stinging cells). They do not play a direct role in muscle contraction. Therefore, this option is incorrect.

4. **Evaluate Nematoblast Cells**: Nematoblasts are specialized cells that contain nematocysts, which are used for capturing prey. They do not contribute to body contraction. Thus, this option is also incorrect.

5. **Evaluate Nutritive Cells**: Nutritive cells are involved in digestion by releasing digestive enzymes. They do not assist in the contraction of the body. Hence, this option is incorrect as well.

6. **Evaluate Epithelial Muscle Cells**: The correct answer lies in the epithelial muscle cells. These cells are responsible for the contraction of Hydra's body. They allow Hydra to move and respond to stimuli by contracting and relaxing. Therefore, this option is correct.

7. **Conclusion**: Based on the analysis, Hydra contracts its body by means of epithelial muscle cells.

### Final Answer:
Hydra contracts its body by means of **epithelial muscle cells**.

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