A biochemist mixed 10 drops of acid with 100 mL of water, and the pH dropped from 7.4 to 5.0. She then mixed 10 drops of acid with 100 mL of blood. The pH dropped from 7.4 to 7.2. What is the reason for this difference?
(a) Blood is thicker than water.
(b) Blood is already very acidic, so the acid has less effect.
(c) Blood is saturated with oxygen; there is little room for acid.
(d) Blood contains buffers that reduce pH change.
