This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which fatty acid is not synthesized by man 
Select and explain. 
A. Linoleic acid, B. Stearic acid, C. Palmitic acid, D. Oleic acid
A: Linoleic acid
Answer: A: Linoleic acid 
Explanation: Linoleic acid 

Humans lack the enzymes to introduce double bonds at carbon atoms beyond C9 in the fatty acid chain.
Hence, humans cannot synthesize linoleic acid and linolenic acid having double bonds beyond C9.
It is worth noting that arachidonic acid can be synthesized only if linoleic acid is provided in the diet.