Which of the following is a colligative property ?

Options

A. Surface tension
B. Viscosity
C. Refractive index
D. Osmotic pressure

Answer

To determine which of the following is a colligative property, we first need to understand what colligative properties are.

### Step-by-Step Solution:

1. **Define Colligative Properties**:
Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent, regardless of the nature of the solute.

2. **List the Common Colligative Properties**:
The main colligative properties include:
- Relative lowering of vapor pressure
- Elevation in boiling point (ΔTb)
- Depression in freezing point (ΔTf)
- Osmotic pressure

3. **Identify Non-Colligative Properties**:
Properties that do not depend on the number of solute particles include:
- Surface tension
- Viscosity
- Refractive index

4. **Analyze the Given Options**:
If the question provides options, we need to check which of them fall under the category of colligative properties.

5. **Conclusion**:
Based on the definitions and properties discussed, the correct answer would be one of the colligative properties listed above. If options C and D are provided as colligative properties, then D is the correct answer.