Osmosis is driven by

Options

A. Concentration of dissolved solutes in a solution
B. Pressure difference
C. Membrane composition
D. Both (1) and (2)

Answer

### Step-by-Step Solution:

1. **Understanding Osmosis**:
- Osmosis is defined as the diffusion of water molecules through a semi-permeable membrane. It specifically involves the movement of solvent (water) from an area of higher concentration to an area of lower concentration.

2. **Factors Affecting Osmosis**:
- Several factors influence the process of osmosis:
- **Concentration of Solute Particles**: The difference in solute concentration on either side of the membrane drives the movement of water.
- **Ionization of Solute Molecules**: The degree to which solute molecules dissociate into ions can affect the osmotic pressure.
- **Temperature**: Higher temperatures can increase the kinetic energy of water molecules, thus influencing the rate of osmosis.
- **Pressure Difference**: The pressure exerted on either side of the membrane can also impact the direction and rate of osmotic movement.

3. **Identifying the Driving Force of Osmosis**:
- The question asks what drives osmosis. The primary driving force is the concentration gradient of dissolved solutes in a solution. This means that osmosis is driven by the difference in solute concentration across the semi-permeable membrane.

4. **Evaluating the Options**:
- Based on the understanding that osmosis is driven by the concentration of dissolved solutes and the factors affecting it, we can conclude that the correct answer is that osmosis is driven by both the concentration of dissolved solutes and the pressure difference.

5. **Final Answer**:
- The correct option is **both one and two** (concentration of dissolved solutes and pressure difference).