Choose the correct option for each question. There is only one correct response for each question.
Which force is called a necessary evil?

Options

A. Gravitational force
B. Electrostatic force
C. magnetic force
D. Frictional force

Answer

To solve the question, "Which force is called a necessary evil?", we will analyze the options and understand the concept of friction.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks us to identify which force is referred to as a "necessary evil". This phrase suggests that the force in question has both beneficial and detrimental effects.

2. **Identifying the Force**: The force that fits the description of a "necessary evil" is friction.

3. **Reasons for Friction Being a Necessary Evil**:
- **Advantages of Friction**:
- Friction is essential for many everyday activities. For example, it allows us to walk without slipping, enables vehicles to grip the road, and is necessary for writing.
- **Disadvantages of Friction**:
- On the other hand, friction can cause wear and tear on machinery and surfaces. It can lead to energy loss in the form of heat, which is often undesirable.

4. **Conclusion**: Based on the analysis, we can conclude that friction is the force referred to as a "necessary evil".

5. **Choosing the Correct Option**: If the options were provided, we would select the one that states "friction" or "frictional force".

### Final Answer:
The correct option is **Frictional Force**.

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