* Exocytosis is the process where cells release substances (like waste products, hormones, or neurotransmitters) from inside the cell to the outside environment. This is done by enclosing the substance in a membrane-bound vesicle that fuses with the cell membrane and releases its contents.

Let's look at why the other options are incorrect:

* Phagocytosis: This is a type of endocytosis where cells engulf large particles (like bacteria) by surrounding them with their cell membrane. This movement is *into* the cell.

* Endocytosis: This is a general term for processes where cells take in substances from the outside environment by engulfing them in a membrane-bound vesicle. This movement is *into* the cell.

* Diffusion: This is the movement of molecules from an area of high concentration to an area of low concentration. It can occur both within the cell and across the cell membrane, but it doesn't necessarily involve a directed movement of materials from inside to outside.

* Osmosis: This is the movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration. It's a specific form of diffusion and doesn't always involve a directed movement of materials from inside to outside.