The correct answer is: A. The hydrophilic head groups of the lipid molecules are exposed to the outside of the cell and the cytoplasm, which is a water-like environment. The hydrophobic tails form an oily layer inside the membrane that keeps water out of the cell.
Plasma membrane of the cell is arranged in a bilayer of phospholipids. Phospholipids are amphipathic molecules which means that they have both hydrophilic and hydrophobic regions. The hydrophilic heads of phospholipids that are faced outward and hydrophobic layer located in the interior of the bilayer together make a good barrier between the interior and exterior of the cell, so the water and other polar or charged substances cannot easily cross the hydrophobic core of the membrane.
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