Answer: The correct answer is- Endocytosis.

Endocytosis can be described as a process in which cell engulfs large molecules from the environment by fusing them with its cell membrane (plasma membrane).

Cell membrane is a selectively permeable, hydrophobic membrane. Large polar molecules ( such as proteins and hormones) can not pass through it by means of simple diffusion.

Cell performs endocytosis for taking in such large molecules.

In this process, plasma membrane first forms a pocket around the target molecule ( such as protein) through invagination and once it completely surrounds the molecule, it is pinched off in the cytoplasm in a form of food vacuole ( phagosome in case of solid particles).

Thus, Endocytosis is the right answer.