**Core Concept**
Hypercalcemia refers to elevated serum calcium levels, which can result from various pathophysiological mechanisms, including increased bone resorption, increased calcium absorption, or decreased renal excretion.

**Why the Correct Answer is Right**
The correct answer is associated with a condition characterized by excessive production of parathyroid hormone (PTH) by the parathyroid glands, leading to increased bone resorption and subsequent hypercalcemia. PTH stimulates osteoclasts to break down bone, releasing calcium into the bloodstream. In addition, PTH increases renal calcium reabsorption and decreases renal phosphate excretion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to a condition known to cause hypercalcemia.
**Option B:** This option is incorrect because it is associated with a condition that typically presents with hypocalcemia, not hypercalcemia.
**Option C:** This option is incorrect because it is associated with a condition that typically presents with hyponatremia, not hypercalcemia.

**Clinical Pearl / High-Yield Fact**
Be aware that hypercalcemia can also be caused by malignancies, such as squamous cell lung cancer, which can produce PTH-related protein (PTHrP), leading to increased bone resorption.

**Correct Answer: C. Primary hyperparathyroidism.**