Final answer:
A situation that would require a buffer is when the stomach has a pH that is too high. Buffers, like the bicarbonate system in the human body or antacids, help to absorb excess hydrogen ions and maintain pH stability.
Step-by-step explanation:
The situation that would require a buffer is B. a stomach with a pH too high. Buffers are critical for maintaining the acid-base homeostasis of the body. A buffer is a solution that can neutralize small amounts of acids or bases in body fluids and thereby maintain a stable pH level. In the human body, the bicarbonate system acts as a buffer to absorb excess hydrogen ions, preventing drastic pH changes. Antacids, which are an example of buffers, function similarly by absorbing hydrogen ions, thus raising the pH of the stomach when it's too high.
An excess of mucus in the lungs, cholesterol in the heart, or a low concentration of water in the kidneys do not directly relate to the acid-base balancing effect of buffers. Hence, these conditions do not typically require a buffer system for correction, unlike a disturbance in the pH balance of the stomach.