Okay, let's tackle this question about the Na+-K+ pump. First, I need to recall what the Na+-K+ pump does. It's an enzyme, right? The sodium-potassium ATPase. Its main function is to pump sodium out of the cell and potassium into the cell, maintaining the concentration gradients. This is crucial for the resting membrane potential and action potentials in neurons.

The question is asking which statement is true about it. Since the options aren't provided, I'll have to think about common facts related to the pump. Let me remember the key points. The pump uses ATP to move 3 Na+ ions out and 2 K+ ions in per cycle. This creates a gradient that's essential for nerve and muscle function. It's also involved in secondary active transport, like in the absorption of glucose in the intestines.

Wait, common misconceptions: sometimes people confuse the number of ions moved. The pump moves 3 Na+ out for every 2 K+ in. Also, it's an example of primary active transport because it directly uses ATP. Another point is that ouabain is a specific inhibitor of this pump. If the question had options about inhibitors, that would be a key point.

Another thing is the pump's role in maintaining osmotic balance. By keeping the sodium out, it prevents too much water from entering the cell. If the pump doesn't work, cells can swell and lyse. Also, the pump contributes to the negative resting membrane potential because more positive ions are pumped out than in.

If the options included something about the direction of ion movement, the correct answer would be the one stating 3 Na+ out and 2 K+ in. If any option said the opposite, that would be wrong. Also, if there's an option about energy source, the correct one would mention ATP hydrolysis.

So, putting this together, the core concept is the function and mechanism of the Na+-K+ ATPase. The correct answer would correctly describe the ion movement ratio, ATP usage, and its role in maintaining gradients. The incorrect options might mix up the numbers, mention passive transport instead of active, or incorrectly state the direction of ion movement.

**Core Concept**
The Na⁺-K⁺ pump (Na⁺/K⁺-ATPase) is a **primary active transport mechanism** that hydrolyzes ATP to move **3 Na⁺ ions out** and **2 K⁺ ions into** the cell, maintaining critical ion gradients essential for **resting membrane potential**, **action potential propagation**, and **cell volume regulation**.

**Why the Correct Answer is Right**
The pump operates via **conformational changes** driven by ATP phosphorylation. For every ATP molecule hydrolyzed, it transports **3 Na⁺ extracellularly** and **2 K⁺ intracellularly**, creating gradients used in **secondary active transport** (e.g., glucose absorption). This process is **ouabain-sensitive** and vital for neuronal excitability and osmotic balance.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect if it states the pump moves 2 Na⁺ out and 3 K⁺ in—reverses the correct ion ratio.
**Option B:** Incorrect if it claims the pump uses passive diffusion—active transport requires ATP, not passive movement.
**Option C:** Incorrect if it attributes the pump

✓ Correct Answer: A. K+ is pumped against the gradient.