Question

which of the following is an example of active transport? diffusion facilitated diffusion osmosis sodium - potassium pump

Explanation:

Active transport requires energy (ATP) to move substances against their concentration gradient. Diffusion, facilitated diffusion, and osmosis are passive transport (no energy, down concentration gradient). The sodium - potassium pump uses ATP to move Na⁺ out and K⁺ into the cell, so it's active transport.

Answer:

D. Sodium - potassium pump (assuming the options are labeled A: Diffusion, B: Facilitated diffusion, C: Osmosis, D: Sodium - potassium pump)