**Core Concept**
Plasma potassium concentration is tightly regulated within a narrow range, and disturbances can lead to life-threatening complications. The kidneys play a crucial role in maintaining potassium homeostasis through the regulation of potassium excretion in the urine. Hyperkalemia, an increase in plasma potassium concentration, can result from various factors, including impaired renal function, potassium overload, or shifts in potassium distribution.

**Why the Correct Answer is Right**
The correct answer is related to the concept of pseudohyperkalemia, a condition that mimics hyperkalemia but is not caused by an actual increase in potassium ions. This occurs when there is an increase in potassium-rich cells or fluids in the blood, which can lead to an artificially elevated plasma potassium concentration. This can be seen in conditions such as hemolysis, where red blood cells rupture and release potassium ions into the bloodstream.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe a condition that increases plasma potassium concentration. While conditions like hypokalemia can lead to shifts in potassium distribution, they do not directly increase plasma potassium concentration.
* **Option B:** This option is incorrect because it refers to a condition that decreases plasma potassium concentration, not increases it.
* **Option C:** This option is incorrect because it is a cause of hypokalemia, not hyperkalemia.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that pseudohyperkalemia can occur in conditions with high potassium-rich cells, such as hemolysis, and can lead to artificially elevated plasma potassium concentrations.

**Correct Answer: D. Hemolysis. Hemolysis**