The correct answer is C. 7.35-7.45.
The pH scale is a logarithmic scale that measures the acidity or alkalinity of a solution. A pH of 7 is considered neutral, a pH below 7 is acidic, and a pH above 7 is alkaline. The pH of human blood is slightly alkaline, with a normal range of 7.35-7.45. This pH is important for maintaining the proper function of cells and tissues. If the pH of blood falls outside of this range, it can lead to serious health problems, such as acidosis or alkalosis.
Option A is incorrect because it is too acidic. A pH of 7.1-7.15 is considered acidic, and can lead to health problems such as acidosis.
Option B is incorrect because it is too alkaline. A pH of 7.45-7.55 is considered alkaline, and can lead to health problems such as alkalosis.
Option D is incorrect because it is too narrow. The normal range of pH for human blood is 7.35-7.45, so option D does not include the entire range.