Select the incorrect statement.

Options

A. (a) If the zero of vernier scale does not coincide with the zero of the main scale, then the vernier calipers is said to be having zero error.
B. (b) Zero correction has a magnitude equal to zero error but sign is opposite to that of zero error.
C. (c) Zero error is positive when the zero of vernier scale lies to the left of the zero of the main scale.
D. (d) Zero error is negative when the zero of vernier scale lies to the left of the zero of the main scale.

Answer

To solve the question of selecting the incorrect statement regarding Vernier calipers, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding Zero Error**:
- The first statement claims that if the zero of the Vernier scale does not coincide with the zero of the main scale, then the Vernier calipers is said to have zero error.
- **Analysis**: This statement is correct. Zero error occurs when the two zeros do not align, indicating a measurement error.

2. **Zero Correction and Zero Error**:
- The second statement states that zero correction has a magnitude equal to zero error, but the sign is opposite to that of zero error.
- **Analysis**: This statement is also correct. Zero correction is used to adjust the reading based on the zero error, and they indeed have equal magnitudes but opposite signs.

3. **Positive Zero Error**:
- The third statement mentions that zero error is positive when the zero of the Vernier scale lies to the left of the zero of the main scale.
- **Analysis**: This statement is correct. If the Vernier scale zero is to the left, it indicates that the reading is showing a positive value when it should be zero, thus resulting in a positive zero error.

4. **Negative Zero Error**:
- The fourth statement claims that zero error is negative when the zero of the Vernier scale lies to the left of the zero of the main scale.
- **Analysis**: This statement is incorrect. If the zero of the Vernier scale lies to the left of the main scale, it indicates a positive zero error, not a negative one.

### Conclusion:
Based on the analysis of each statement, the incorrect statement is the fourth one. Therefore, the answer to the question is option D.

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