The purpose of the plasma membrane is to keep certain things and things out. So the correct answer to this questions is D, encloses specific structures.
The correct answer would be D. encloses specific structures.
The plasma membrane or the cell membrane acts like the boundary which separates the cell from its surrounding.
It surrounds or encloses the cytoplasm (contains specific organelles or structures) of the cell and thus physically separate the intracellular components from the external or extracellualar environment.
The phospholipid bilayer structure of the membrane provides the semi-permeable nature to it. It controls the movement of substances in and out of the cell.
