**Core Concept**
Tumor lysis syndrome (TLS) is a life-threatening condition that occurs when a large number of cancer cells die rapidly, releasing their contents into the bloodstream. This leads to a complex array of electrolyte and metabolic disturbances.

**Why the Correct Answer is Right**
Tumor lysis syndrome is characterized by the release of intracellular contents, including potassium (K+), phosphate (PO4^2-), and nucleic acids. The breakdown of nucleic acids leads to the formation of uric acid, which is a key component of TLS. The rapid release of potassium ions into the bloodstream can cause hyperkalemia, while the breakdown of nucleic acids and the subsequent formation of uric acid can cause hyperuricemia. The correct answer, C (ad), includes both hyperkalemia (a) and hyperuricemia (d) as true statements about TLS.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypercalcemia is not typically associated with TLS. In fact, TLS is more commonly associated with hypocalcemia due to the release of phosphate ions into the bloodstream, which can bind to calcium ions and decrease their levels.

**Option B:** Lactic acidosis is not a characteristic feature of TLS. TLS is more commonly associated with hyperphosphatemia, hyperkalemia, and hyperuricemia.

**Option D:** Hypercalcemia is not typically associated with TLS, as mentioned earlier.

**Clinical Pearl / High-Yield Fact**
When managing patients with TLS, it's essential to monitor electrolyte levels closely, particularly potassium, phosphate, and magnesium. Early recognition and intervention can help prevent the development of life-threatening complications such as cardiac arrhythmias and acute kidney injury.

**✓ Correct Answer: C. ad. Both hyperkalemia and hyperuricemia are true statements about tumor lysis syndrome.**