The correct option is D Arachidonic acid
Unsaturated fatty acids have single or multiple double bonds in between carbon atoms. Due to the presence of double bonds, they have lower melting point.
They are mostly liquids at room temperature. They are mostly obtained from plants. They are found in sunflower oil, olive oil. They include arachidonic acid (20C), linoleic acid, linolenic acid.
Arachidonic acid is an essential fatty acid (EFA) and is involved in the synthesis of prostaglandins. Prostaglandins are a group of compounds (which are basically lipids) which function as hormones in animals.