AIIMS 2018 Biology pH Levels MCQ Question

Human blood has the highest pH among the given options, typically ranging from 7.35 to 7.45, which is slightly alkaline due to the presence of bicarbonate ions (HCO₃⁻) that help maintain acid-base balance. In contrast, human saliva has a pH around 6.5 to 7.5, gastric juice is highly acidic with a pH of 1.5 to 3.5 due to hydrochloric acid (HCl), and urine generally has a pH between 4.5 and 8.0, depending on diet and hydration. Thus, blood's higher pH reflects its critical role in maintaining homeostasis in the body.