pH scale was introduced byA. SorenSenB. NewtonC. ChadwickD. Roentgen

The pH scale was introduced by **Soren Sorensen**.

### Explanation:

1. **Background of pH Scale**:
- The pH scale measures the acidity or alkalinity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline (basic).

2. **Who is Soren Sorensen?**:
- Soren Sorensen was a Danish chemist who introduced the pH scale in 1909 while working at the Carlsberg Laboratory in Copenhagen. He developed this scale to provide a simple way to express the concentration of hydrogen ions (\(H^+\)) in a solution.

3. **Why Other Options are Incorrect**:
- **Newton**: Sir Isaac Newton was a mathematician and physicist known for his laws of motion and gravity, not for contributions to chemistry.
- **Chadwick**: James Chadwick is known for discovering the neutron, which is unrelated to the pH scale.
- **Roentgen**: Wilhelm Conrad Roentgen is known for discovering X-rays and had no direct contribution to the pH concept.

### Conclusion:
Therefore, the correct answer is **A. Soren Sorensen**.