Contractile vacuoles help in

Options

A. excretion
B. osmoregulation
C. osmoregulation and respiration
D. digestion

Answer

### Step-by-Step Solution:

1. **Understanding Contractile Vacuoles**:
- Contractile vacuoles are specialized cell organelles found in certain organisms, including protozoans, sponges, and hydras.

2. **Function of Contractile Vacuoles**:
- The primary function of contractile vacuoles is to manage the water balance within the cell. They do this by expelling excess water that accumulates inside the cell.

3. **Mechanism of Action**:
- When the internal pressure of the cell increases due to excess water, the contractile vacuole contracts and expels this water into the external environment.

4. **Additional Function**:
- Besides regulating water, contractile vacuoles also help in the excretion of nitrogenous wastes, particularly ammonium ions.

5. **Role in Osmoregulation**:
- The processes of expelling excess water and nitrogenous wastes are crucial for maintaining osmotic balance within the cell, which is referred to as osmoregulation.

6. **Conclusion**:
- Therefore, the primary role of contractile vacuoles is in osmoregulation, helping to maintain the cell's internal environment.

### Final Answer:
Contractile vacuoles help in osmoregulation.

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