Why do phospholipids spontaneously form a bilayer when placed in water?

• A. Because the phosphate head groups are nonpolar and pack together in the bilayer interior.
• B. Because covalent bonds form between phospholipid tails, creating a permanent two-layer sheet.
• C. Because their amphipathic structure drives hydrophobic tails to avoid water while hydrophilic heads interact with water, minimizing free energy.
• D. Because water molecules are nonpolar and preferentially dissolve the fatty acid tails, forcing heads outward.

Answer: (C)