Which one of the following is correctly matched?

Options

A. Emulsion - Curd
B. Foam - mist
C. Aerosol - smoke
D. Solid sol - Butter

Answer

To determine which of the given options is correctly matched, we will analyze each option based on the definitions and examples of colloidal systems.

### Step-by-Step Solution:

1. **Option 1: Emulsion - Curd**
- An emulsion is a colloidal system where both the dispersed phase and the dispersion medium are liquids. Common examples include milk and butter. Curd, however, is not a typical example of an emulsion; it is a gel-like substance formed from the coagulation of milk proteins. Therefore, this option is **incorrect**.

2. **Option 2: Foam - Mist**
- A foam is a colloidal system in which gas is dispersed in a liquid. Mist, on the other hand, is a colloidal system where tiny droplets of liquid (water) are dispersed in air (gas). Since mist does not represent a foam (which should be gas in liquid), this option is also **incorrect**.

3. **Option 3: Aerosol - Smoke**
- An aerosol is a colloidal system where solid or liquid particles are dispersed in a gas. Smoke is a classic example of an aerosol, as it consists of solid particles (carbon) dispersed in air (gas). Therefore, this option is **correct**.

4. **Option 4: Solid Sol - Butter**
- A solid sol is a colloidal system where solid particles are dispersed in a solid medium. Butter is not an example of a solid sol; it is more accurately classified as an emulsion. Therefore, this option is **incorrect**.

### Conclusion:
The only correctly matched option is **Option 3: Aerosol - Smoke**.