Which statement best explains why linoleic acid (LA) is considered essential in the human diet?

• A. Because LA is a saturated fatty acid necessary for maintaining membrane rigidity and cannot be obtained from plants
• B. Because LA is efficiently converted into DHA in humans, so dietary LA is sufficient to meet DHA needs even without fish consumption
• C. Because LA is the only lipid used to synthesize cholesterol in the liver and must be consumed daily in large amounts
• D. Because humans cannot synthesize the double bond at the omega‑6 position and LA serves as a dietary precursor for arachidonic acid and downstream eicosanoids

Answer: (D)