The correct option is C. Osmosis. Detailed Explanation: What is Osmosis? Osmosis is the process by which water molecules move across a semi-permeable membrane. This movement 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 goal of osmosis is to equalize the solute concentrations on both sides of the membrane. Why is Osmosis the Correct Answer? 1. Semi-Permeable Membrane: Osmosis specifically involves a semi-permeable membrane that allows water to pass through but restricts the movement of solute particles. This characteristic is crucial because it differentiates osmosis from other processes.

1. Concentration Gradient: The movement of water in osmosis is driven by the concentration gradient of solutes. Water moves to dilute the area with a higher concentration of solute, thereby attempting to balance the concentrations on both sides of the membrane.
2. Passive Process: Osmosis is a passive process, meaning it does not require energy (ATP) to occur. Water moves naturally down its concentration gradient.

Why the 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 and moves water along its concentration gradient, not against it. B. Facilitated Diffusion - Definition: Facilitated diffusion is the process by which substances move across a membrane with the help of transport proteins, but still down their concentration gradient. - Why It's Wrong: While facilitated diffusion involves the movement of molecules down their concentration gradient, it does not specifically refer to the movement of water. Osmosis is the specific term for water movement. D. Simple Diffusion - Definition: Simple diffusion is the movement of small or nonpolar molecules across a membrane directly, without the need for transport proteins, and also down their concentration gradient. - Why It's Wrong: Simple diffusion does not specifically involve water and does not occur through a semi-permeable membrane in the same way osmosis does. Summary of Key Points:

• Osmosis is the movement of water from an area of lower solute concentration to an area of higher solute concentration across a semi-permeable membrane.
• It is a passive process that does not require energy.
• Active transport and facilitated diffusion involve different mechanisms and energy requirements, while simple diffusion does not specifically pertain to water movement.
• Understanding osmosis is crucial for grasping concepts related to cell biology, such as how cells maintain homeostasis and manage their internal environments.