Osmosis is

Options

A. passage of solvent only through a semipermeable membrane
B. passage of solutes only through a membrane
C. passage of both solvent and solute through a membrane
D. passage of solution through a protoplasm.

Answer

**Step-by-Step Solution:**

1. **Understanding Osmosis**: Osmosis is defined as the movement of water molecules (the solvent) through a semi-permeable membrane. This membrane allows only certain molecules to pass through while blocking others.

2. **Direction of Movement**: Water moves from an area of higher concentration (more water, less solute) to an area of lower concentration (less water, more solute). This movement continues until equilibrium is reached.

3. **Role of Semi-Permeable Membrane**: The semi-permeable membrane is crucial in osmosis as it selectively allows the passage of water while restricting solutes. This characteristic is what differentiates osmosis from other types of transport.

4. **Endosmosis and Exosmosis**:
- **Endosmosis** refers to the absorption of water into the cell, which increases the internal turgor pressure and helps maintain cell shape.
- **Exosmosis** is the process where water exits the cell, which can lead to a decrease in turgor pressure.

5. **Conclusion**: Based on the definition and characteristics of osmosis, the correct answer to the question "Osmosis is" is "the passage of solvent only through a semi-permeable membrane."

**Final Answer**: Osmosis is the passage of solvent only through a semi-permeable membrane.

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