What is the measure of acidity with a scale from 1 to 14, where values below 7 indicate acidity?

• A. pH
• B. Haemoglobin
• C. Myoglobin
• D. A-VO2 Difference

Answer: (A)

pH is the measure of how acidic or basic a solution is. It uses a 0–14 scale, with 7 being neutral; values below 7 indicate acidity because they reflect a higher hydrogen ion concentration. The lower the pH, the stronger the acidity. This concept applies to many environments, including blood, where pH affects enzyme activity and oxygen delivery. The other terms are not measures of acidity: haemoglobin and myoglobin are proteins that bind and store oxygen, while A-VO2 difference relates to how much oxygen is extracted by tissues, not how acidic the environment is.