When taking pH measurements of solutions, why is it important to stir thoroughly after adding each reagent? Select one:
A. Mixing helps ensure that the measured pH is reflective of the entire solution.
B. Mixing helps keep the solution components from contaminating the pH meter.
C. Mixing helps prevent precipitation of insoluble salts out of solution.
D. A pH meter can only measure ions that are flowing past the meter at a fast speed.