**Core Concept**
The question is testing the management of hyperkalemia, a condition characterized by elevated potassium levels in the blood. The classic ECG finding in hyperkalemia is tall peaked T waves, which is a sign of cardiac membrane depolarization. The management of hyperkalemia involves stabilizing cardiac membranes, shifting potassium into cells, and removing excess potassium from the body.

**Why the Correct Answer is Right**
The correct answer involves administering calcium gluconate, which helps to stabilize cardiac membranes and counteract the effects of hyperkalemia. Calcium ions bind to the cardiac membrane, reducing the risk of cardiac arrhythmias and conduction delays. This is a critical step in managing hyperkalemia, as it helps to prevent cardiac complications. Additionally, administering calcium gluconate does not actually lower potassium levels, but it helps to protect the heart from the effects of hyperkalemia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Administering insulin and glucose would help to shift potassium into cells, but it would not provide immediate protection to cardiac membranes. This is a delayed effect and not the first line of treatment.
* **Option B:** Administering sodium bicarbonate would help to shift potassium into cells, but it would not provide immediate protection to cardiac membranes and is not a first-line treatment for hyperkalemia.
* **Option D:** Administering potassium-lowering medications such as Kayexalate would help to remove excess potassium from the body, but they do not provide immediate protection to cardiac membranes and are not a first-line treatment for hyperkalemia.

**Clinical Pearl / High-Yield Fact**
When managing hyperkalemia, remember that calcium gluconate should be administered immediately to protect cardiac membranes, followed by measures to shift potassium into cells and remove excess potassium from the body.

**Correct Answer:** C. Calcium gluconate.