The correct option is C. Osmosis. Detailed Explanation: What is Osmosis? Osmosis is the movement of water molecules across a semipermeable membrane. This process occurs from an area of lower solute concentration (where there are fewer solute particles) to an area of higher solute concentration (where there are more solute particles). The semipermeable membrane allows water molecules to pass through but restricts the movement of solute particles. Why is Osmosis Important? Osmosis is a vital process in biological systems. It helps maintain cell turgor pressure, regulates the internal environment of cells, and is crucial for nutrient absorption and waste removal in organisms. Step-by-Step Explanation of Osmosis: 1. Concentration Gradient: In a solution, solute concentration can vary. When two solutions with different solute concentrations are separated by a semipermeable membrane, a concentration gradient is established.

1. Water Movement: Water molecules will naturally move from the area with a lower concentration of solute (more water relative to solute) to the area with a higher concentration of solute (less water relative to solute). This movement continues until equilibrium is reached, meaning the concentrations of solute on both sides of the membrane become equal.
2. Equilibrium: At equilibrium, the net movement of water molecules stops, but water continues to move in both directions across the membrane at equal rates.

Why Other Options Are Incorrect: A. Active Transport - Definition: Active transport is the movement of molecules across a membrane against their concentration gradient, which requires energy (usually in the form of ATP). - Why It's Wrong: Osmosis does not require energy; it is a passive process driven by the concentration gradient of water and solutes. Therefore, this option does not describe the movement of water. B. Facilitated Diffusion - Definition: Facilitated diffusion is the process by which molecules pass through a cell membrane via special proteins (transport proteins) without the use of energy, moving down their concentration gradient. - Why It's Wrong: While facilitated diffusion involves the movement of molecules down their concentration gradient, it specifically refers to solutes (like glucose or ions) and not water. Osmosis specifically pertains to the movement of water. D. Endocytosis - Definition: Endocytosis is a process by which cells engulf substances from their external environment, forming a vesicle to bring them into the cell. This process requires energy. - Why It's Wrong: Endocytosis is not related to the movement of water across a membrane. It involves the uptake of larger particles or fluids and is not a passive process like osmosis. Summary:

• Osmosis is the movement of water from an area of lower solute concentration to an area of higher solute concentration across a semipermeable membrane.
• It is a passive process that does not require energy.
• Other processes like active transport, facilitated diffusion, and endocytosis involve different mechanisms and are not specific to water movement.
• Understanding osmosis is crucial for grasping how cells maintain homeostasis and manage their internal environments.

Revision Points:

• Osmosis is specific to water movement across a semipermeable membrane.
• It occurs from low solute concentration to high solute concentration.
• It is a passive process, unlike active transport which requires energy.
• Recognizing the differences between osmosis and other transport mechanisms is essential for understanding cellular processes.