Answer:
D
Step-by-step explanation:
A is not possible because osmosis is a term given only for the movement of water down it's potential through a partially permeable membrane.
B is not possible since the molecule is big and since it's an antibody, it's polar. It being polar makes it impossible to passively cross the phospholipid bilayer of the cell membrane.
C is not possible because it describes the action of something bulky leaving the cells, not entering them.
Endocytosis is the uptake of large molecules into the cells by forming phagocytic or pinocytic vesicles.