Which one of the following statements is true ?

Options

A. A scalar quantity is the one that is conserved in a process.
B. A scalar quantity is the one that can never take negative values.
C. A scalar quantity is the one that does not vary from one point to another in space .
D. A scalar quantity has the same value for observers with different orientations of the axes.

Explanation

To solve the question regarding which statement about scalar quantities is true, we will analyze each option systematically.

### Step-by-step Solution:

1. **Understanding Scalar Quantities**:
- Scalar quantities are physical quantities that have magnitude but no direction. Examples include mass, temperature, and speed.

2. **Analyzing Option 1**:
- **Statement**: "A scalar quantity is the one that is conserved in a process."
- **Analysis**: This statement is incorrect. Not all scalar quantities are conserved. For example, speed can change depending on the medium (like the speed of light in different media).

3. **Analyzing Option 2**:
- **Statement**: "A scalar quantity is the one that can never take negative values."
- **Analysis**: This statement is also incorrect. Scalar quantities can take negative values. For instance, electric charge is a scalar quantity and can be positive or negative.

4. **Analyzing Option 3**:
- **Statement**: "A scalar quantity is the one that does not vary from one point to another in space."
- **Analysis**: This statement is incorrect as well. Scalar quantities can vary from one point to another. For example, temperature can vary from one location to another.

5. **Analyzing Option 4**:
- **Statement**: "A scalar quantity has the same value for observers with different orientations of the axis."
- **Analysis**: This statement is true. Scalar quantities are independent of the orientation of the coordinate system. For instance, mass remains the same regardless of how you look at it.

### Conclusion:
The correct answer is **Option 4**: "A scalar quantity has the same value for observers with different orientations of the axis."

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