The cell membrane(or plasma membrane) is the outermost covering of a cell it protects the cell from the external environment it is

An image of plasma membrane shows the phospholipid bilayer, embedded proteins, and cholesterol molecules. The membrane separates the extracellular space, outside of the cell, from the cytosol inside the cell. The plasma membrane is the border between the interior and exterior of a cell. I hope this helps you :)

prism b but im not for sure