The correct answer is c) the non polar lipid bilayer.
The cell membrane, or plasma membrane, is primarily composed of a double layer of phospholipids, which contain both polar and non-polar regions. The non-polar lipid bilayer forms a barrier that is hydrophobic (water-repelling), preventing water and other polar molecules from easily passing through it. While the polar phosphate groups face outward and interact with the aqueous environment, the non-polar tails create a middle layer that restricts water’s entry into the cell.