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 to an area of higher solute concentration. This movement occurs in order to equalize solute concentrations on both sides of the membrane. The selectively permeable membrane allows water to pass through while restricting the movement of solutes (like salts or sugars). Why is Osmosis the Correct Answer? 1. Concentration Gradient: Osmosis specifically refers to the movement of water in response to a concentration gradient. When there is a difference in solute concentration across a membrane, water will move toward the area with a higher concentration of solutes to dilute it. This is a fundamental concept in biology, particularly in understanding how cells maintain homeostasis.

1. Selectively Permeable Membrane: The term "selectively permeable" indicates that the membrane allows certain substances to pass while blocking others. In the case of osmosis, the membrane is permeable to water but not to the solutes, which is crucial for the process to occur.
2. Passive Process: Osmosis is a passive transport process, meaning it does not require energy (ATP) to occur. Water moves naturally down its concentration gradient, which is a key characteristic of passive transport mechanisms.

Why the Other Options are Incorrect: A. Active Transport: - Active transport is the movement of substances against their concentration gradient, which requires energy (ATP). In contrast to osmosis, active transport is not about the movement of water but rather the movement of ions or molecules from an area of lower concentration to an area of higher concentration. Therefore, this option does not describe the movement of water. 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 does not require energy and can occur down a concentration gradient, it typically refers to solutes (like glucose or ions) rather than water. Thus, it does not accurately describe the process of water movement. 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 due to a concentration gradient. 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 due to 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 across a membrane due to concentration differences.
• It occurs passively, without energy, and targets solute concentration equalization.
• Active transport, facilitated diffusion, and endocytosis are distinct processes not related to water movement in this context.