**Core Concept**
The kidneys play a crucial role in maintaining electrolyte balance, acid-base homeostasis, and fluid volume regulation through the regulation of renal excretion and reabsorption of various substances. The kidneys achieve this through complex mechanisms involving ion channels, transporters, and enzymes.

**Why the Correct Answer is Right**
The kidneys regulate potassium levels by adjusting the amount of potassium excreted in the urine. This process is primarily mediated by the sodium-potassium pump (Na+/K+-ATPase) in the renal tubules, which maintains a delicate balance between potassium reabsorption and secretion. Additionally, the kidneys use the aldosterone-sensitive distal convoluted tubule (DCT) to fine-tune potassium excretion in response to changes in serum potassium levels.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the kidneys' role in potassium regulation.
**Option B:** While the kidneys do play a role in acid-base balance, this option is not specific to potassium regulation.
**Option C:** This option might be related to other kidney functions, but it is not the correct answer regarding potassium regulation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the kidneys can compensate for acute potassium shifts by adjusting potassium excretion, but chronic potassium imbalances can lead to serious complications, including cardiac arrhythmias.

**Correct Answer:** C.