Answer: B) lipid
Explanation:
The molecule that makes up the double layer of a cell membrane is the lipid. The lipids are the biomolecules which are soluble in non-polar solvents. The lipids form a semipermeable membrane. The lipid bilayer allows the passage of small hydrophobic molecules and gases like carbon dioxide and oxygen across the cell. Small polar molecules such as water and ethanol also pass through the membrane but slowly. It restricts the diffusion of large molecules, ions, amino acids and sugars across the cell membrane.
