Diesel is used in:

Options

A. cooling oil
B. paints
C. road surfacing
D. electric generators

Explanation

**Step-by-Step Solution:**

1. **Understanding Diesel**: Diesel is a petroleum product derived from the refining of crude oil. It is primarily used as a fuel.

2. **Analyzing the Options**:
- **Cooling Oil**: Diesel is not used as a cooling oil. Cooling oils are typically used in engines to dissipate heat, while diesel serves as fuel.
- **Paints**: Diesel is not used in the production of paints. Paints are made from different types of solvents and resins, not diesel.
- **Road Surfacing**: While petroleum products are used for road surfacing, specifically bitumen, diesel itself is not used for this purpose.
- **Electric Generators**: Diesel is commonly used as fuel in electric generators. It undergoes combustion to produce energy, which is then converted into mechanical energy to generate electricity.

3. **Conclusion**: Among the options provided, diesel is primarily used in electric generators.

**Final Answer**: Diesel is used in electric generators.

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