The correct option is C. Osmosis. Detailed Explanation: What is Osmosis? Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration). This movement continues until there is an equal concentration of solute on both sides of the membrane, achieving equilibrium. Why is Osmosis the Correct Answer? 1. Selectively Permeable Membrane: Osmosis specifically involves the movement of water through a membrane that allows certain molecules to pass while restricting others. In biological systems, cell membranes are selectively permeable, allowing water to move freely while controlling the passage of solutes.

1. Concentration Gradient: The driving force behind osmosis is the concentration gradient of solutes. Water moves to balance the concentration of solutes on either side of the membrane. For example, if one side of the membrane has a high concentration of salt (solute), water will move from the side with lower salt concentration to the side with higher salt concentration.
2. Passive Process: Osmosis is a passive process, meaning it does not require energy (ATP) to occur. The movement of water is driven solely by the concentration gradient, making it a natural and spontaneous process.

Why the Other Options are Incorrect: A. Active Transport: - Active transport is the movement of molecules across a membrane against their concentration gradient, which requires energy (usually in the form of ATP). Since osmosis involves movement along the concentration gradient (from high to low concentration), it does not fit the definition of active transport. B. Facilitated Diffusion: - Facilitated diffusion is a type of passive transport that involves the movement of molecules across a membrane via specific transport proteins. While it also does not require energy and moves along the concentration gradient, it primarily refers to solutes (like glucose or ions) rather than water. Therefore, it is not the best description of the movement of water molecules. D. Endocytosis: - Endocytosis is a process by which cells engulf substances from their external environment, bringing them into the cell in vesicles. This process requires energy and is not related to the movement of water across a membrane. It is more about the uptake of larger molecules or particles rather than the passive movement of water. Summary of Key Points:

• Osmosis is the movement of water across a selectively permeable membrane driven by a concentration gradient.
• It occurs from an area of lower solute concentration to an area of higher solute concentration.
• Osmosis is a passive process that does not require energy.
• Other options (active transport, facilitated diffusion, endocytosis) do not accurately describe the movement of water in this context.

Revision Summary:

• Osmosis is the movement of water through a selectively permeable membrane.
• It occurs along a concentration gradient (from low to high solute concentration).
• Osmosis is a passive process, unlike active transport which requires energy.
• Understanding the differences between osmosis and other transport mechanisms is crucial for grasping cellular processes.