Which of the following is an example of osmosis?

• A. Sodium ions are pumped out of a cell against their concentration gradient using ATP.
• B. Oxygen gas moves from the alveoli into the bloodstream down its concentration gradient.
• C. Glucose molecules move from an area of high concentration to an area of low concentration through a membrane protein channel.
• D. Water molecules move across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Answer: (D)