Which of the following are correctly matched ?

Options

A. Butter-gel
B. Milk-emulsion
C. For-aerosol
D. Dust-Solid sol

Explanation

To determine which of the options are correctly matched, let's analyze each one based on the definitions of the terms involved.

1. **Butter is a gel**:
- Butter is indeed a gel-like substance. It has a semi-solid consistency and can be classified as a gel because it consists of fat droplets dispersed in a continuous phase, which is mostly water.
- **Conclusion**: This option is correctly matched.

2. **Milk is an emulsion**:
- Milk is a classic example of an emulsion, which is a mixture of two immiscible liquids (in this case, fat and water) where one liquid is dispersed in the other.
- **Conclusion**: This option is correctly matched.

3. **Foam is a solid**:
- Foam is not a solid; it is a colloidal system where gas bubbles are dispersed in a liquid or solid. Foams can be found in various forms, such as whipped cream (liquid foam) or Styrofoam (solid foam), but they are not classified as solids in the traditional sense.
- **Conclusion**: This option is incorrectly matched.

4. **Dust is a solid**:
- Dust consists of solid particles that are suspended in the air. It is indeed made up of solid matter.
- **Conclusion**: This option is correctly matched.

### Summary of Correct Matches:
- **Correctly Matched**:
1. Butter is a gel (True)
2. Milk is an emulsion (True)
3. Dust is a solid (True)
- **Incorrectly Matched**:
3. Foam is a solid (False)

### Final Answer:
Options 1, 2, and 4 are correctly matched, while option 3 is incorrectly matched.