Okay, let's tackle this question. The user is asking about an example of active transport. First, I need to recall what active transport is. Active transport is the movement of molecules across a cell membrane from a lower concentration to a higher concentration, which requires energy, usually in the form of ATP. So, the key here is that it's against the concentration gradient and needs energy.

Now, the options aren't provided, but common examples of active transport include the sodium-potassium pump, glucose absorption in the intestines via the SGLT1 transporter, and the calcium pump in muscle cells. The sodium-potassium pump is a classic example because it moves sodium out and potassium into the cell against their gradients using ATP.

For the incorrect options, passive transport examples like diffusion or facilitated diffusion don't require energy. Osmosis is a type of passive transport. So if any option mentions osmosis or simple diffusion, those would be wrong. Also, some might confuse endocytosis or exocytosis as active transport, but those are bulk transport mechanisms that also require energy but are different mechanisms.

The clinical pearl here is to remember that active transport is energy-dependent and against the concentration gradient. A mnemonic could be "Active transport = Against the gradient, ATP needed." The sodium-potassium pump is a high-yield fact for exams because it's fundamental and involved in maintaining resting membrane potential.

**Core Concept**
Active transport is the movement of molecules across a cell membrane **against their concentration gradient**, requiring energy (usually ATP). It involves specific carrier proteins, such as ion pumps or symporters, to facilitate this process.

**Why the Correct Answer is Right**
The sodium-potassium pump (Na⁺/K⁺-ATPase) is a classic example of active transport. It uses ATP to move **3 Na⁺ out of the cell** and **2 K⁺ into the cell**, maintaining electrochemical gradients critical for nerve impulses, muscle contraction, and osmoregulation. This process is **primary active transport** because ATP directly powers the transport.

**Why Each Wrong Option is Incorrect**
**Option A:** Osmosis (passive, water movement across a semipermeable membrane) does not require energy or carriers.
**Option B:** Simple diffusion (passive, no energy required) occurs along the concentration gradient without carrier proteins.
**Option C:** Facilitated diffusion (passive) uses carriers but does not require energy; it follows the concentration gradient.

**Clinical Pearl / High-Yield Fact**
Always associate **active transport** with **ATP consumption** and **gradient reversal**. The sodium-potassium pump is a **NEET/USMLE favorite**—remember: **3 Na⁺ out, 2 K⁺ in, ATP hydrolyzed**. Contrast this with **secondary active transport** (e.g., glucose reabsorption in kidneys), where energy from Na⁺ gradients drives other molecules.

**Correct Answer: C. Sodium-potassium pump**

✓ Correct Answer: C. Cotranspo of amino-acids with Na+