**Core Concept**
The sodium-potassium pump is a transmembrane protein that utilizes ATP hydrolysis to actively transport three sodium ions out of a cell and two potassium ions into the cell, maintaining the cellular electrolyte balance and membrane potential.

**Why the Correct Answer is Right**
The sodium-potassium pump is an example of active transport, where energy is required to move ions against their concentration gradient. The pump uses ATP to drive this process, pumping sodium out of the cell and potassium into the cell against their respective concentration gradients. This process is crucial for maintaining the resting membrane potential and cellular homeostasis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the sodium-potassium pump does not function through facilitated diffusion, which relies on concentration gradients without energy input.
**Option B:** This option is incorrect as the sodium-potassium pump is not an example of passive transport, which relies on concentration gradients without energy input.
**Option C:** This option is incorrect as the sodium-potassium pump does not function through osmosis, which is the movement of water across a semipermeable membrane.

**Clinical Pearl / High-Yield Fact**
The sodium-potassium pump is essential for maintaining the resting membrane potential, and its dysfunction can lead to various cardiac and neurological disorders.

**Correct Answer:** C. Active transport