The plasma membrane or the cell
membrane is the one that protects the cytoplasm of a cell. It is mostly
composed of lipids and proteins. It has a phospholipid bilayer that controls
the entering and exiting of molecules in the cell and at the same time,
provides protection for the cell or plasma membrane. Proteins embedded within
the phospholipid bilayer have the same function of the plasma membrane that
includes selective transport. The phospholipid bilayer consists mainly of the
lipid molecules. The answer is letter B.
