The correct answer is option 3: Endosmosis. When a cell becomes turgid, it means that it has gained water and swelled up due to an inward flow of water. Endosmosis is the process in which water molecules move from an area of lower solute concentration to an area of higher solute concentration through a selectively permeable membrane. This causes the cell to swell and become turgid.

Option 1: Plasmolysis is the opposite process, where water moves out of the cell, causing it to shrink and become plasmolyzed. This is not the correct answer for the given question.

Option 2: Exosmosis is also the opposite process, where water moves out of the cell. This is not the correct answer for the given question.

Option 4: Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration. While diffusion does contribute to water movement, it does not specifically explain why a cell becomes turgid. Therefore, this is not the correct answer for the given question.

In conclusion, the correct answer is option 3: Endosmosis, where water moves into the cell, causing it to become turgid.