Cell fractionation is the technique which allows different cells part to be separated from each other on the basis of their density gradient by using a centrifuge.
In cell fractionation, first the cell wall and membrane of cells are broken by chemical, physical or mechanical method. Then the cell component can be separated by centrifuging them at different rpm.
Components that have higher density can be found in the bottom and the light density can be found on top of the tube. Therefore the correct answer is c. cell fractionation.
The mode of nutrition described above is phagocytosis. Amooba is a unicellular eukaryotes and it obtains its nutrition using the same method. Amoeba feeds on microscopic organisms, which it engulfs, secretes into its food vacuole and digest.