What is the function of contractile vacuole?

Explanation

### Step-by-Step Solution:

1. **Understanding Vacuoles**:
- Vacuoles are membrane-bound spaces found within the cytoplasm of cells. They serve various functions depending on the type of cell.

2. **Composition of Vacuoles**:
- Vacuoles typically contain water, sap, and various excretory products. They can also store substances that are not useful for the cell.

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