Which option best defines osmosis in the context of passive transport across biological membranes?

• A. The net movement of solute molecules across a membrane from lower solute concentration to higher solute concentration using ATP
• B. The net movement of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration (higher water potential to lower water potential)
• C. The movement of any molecules across a membrane through transport proteins down their electrochemical gradient
• D. The bulk flow of fluid driven by a pressure gradient (hydrostatic pressure) through a tube or tissue

Answer: (B)