Final answer:
The pH scale is a measure of the acidity or basicity of a solution, ranging from 0 to 14. The optimum pH level for blood in the human body is around 7.4, which is slightly alkaline.
Step-by-step explanation:
The pH scale is a measure of the acidity or basicity of a solution, ranging from 0 to 14. Anything below 7 is acidic, while anything above 7 is alkaline. The optimum pH level varies depending on the context. In the human body, for example, the optimum pH level for blood is around 7.4, which is slightly alkaline.