The correct option is D Endocytosis
Exocytosis is a process in which the vesicle containing small particle is formed inside the cell, which then release the contents outside the cell by fusion of cell membrane and vesicular membrane. This way is not used by Amoeba to obtain its food.
Plasmolysis is a process in which when a cell is placed in a hypertonic solution then due to exosmosis the cell lose water and cell will shrink. This way is not used by Amoeba to obtain its food.
Endocytosis is a process in which cells absorb molecules by of engulfing them. Cells use this mechanism when the molecules are larger and polar hence, cannot pass through hydrophobic cell membrane.
The process shows engulfment of small food particles by forming an invagination around it then forming a small vesicle. This vesicle is then taken inside the cell and then vesicle is broken down to release the food particle.