Osmosis requires

Options

A. Water potential gradient
B. Plasma membrane
C. Living systems
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding Osmosis**:
- Osmosis is a specific type of diffusion that involves the movement of solvent molecules, primarily water, through a semi-permeable membrane.

2. **Key Characteristics of Osmosis**:
- **Solvent Movement**: Water molecules move from an area of higher water concentration (or lower solute concentration) to an area of lower water concentration (or higher solute concentration).
- **Semi-Permeable Membrane**: Osmosis occurs through a semi-permeable membrane, which allows only the solvent (water) to pass through while restricting the movement of solute particles.

3. **Requirements for Osmosis**:
- **Water Potential Gradient**: A difference in water potential is necessary for osmosis to occur. Water moves from a region of higher water potential to a region of lower water potential.
- **Plasma Membrane**: The presence of a semi-permeable membrane, such as the plasma membrane of cells, is essential for the process of osmosis.
- **Living System**: Osmosis is a process that occurs in living systems, as it is crucial for maintaining cellular functions and homeostasis.

4. **Conclusion**:
- Therefore, osmosis requires all of the following: a water potential gradient, a semi-permeable membrane (like the plasma membrane), and it occurs in living systems. Thus, the correct answer is "all of the above".