Spoilage of oil can be detected by which fatty acid:

The correct option is D Erucic acid
Erucic acid is a monounsaturated omega-9 fatty acid. It is present in high concentrations in oils and is easily broken down y microorganisms to produce a foul odour.
hence, its presence can be used to detect the spoilage of oils.
Oleic acid is an unsaturated fatty acid and is the most widely distributed and abundant fatty acid in nature.
Linolenic acid is a fatty acid that is found in plants and involved in the formation of prostaglandins.
Linoleic Acid is a polyunsaturated essential fatty acid found mostly in plant oils. It is used in the biosynthesis of prostaglandins and cell membranes