Prostaglandins are: (A) Monounsaturated fatty acids, (B) Polyunsaturated fatty acids, (C) Eicosanoids, (D) Saturated fatty acids
Answer is C. Unsaturated Fatty Acids Contain One or More Double Bonds
Unsaturated fatty acids may be further subdivided as follows:

Monounsaturated (monoethenoid, monoenoic) acids, containing one double bond.
Polyunsaturated  (polyethenoid,  polyenoic)  acids,  containing two or more double bonds.
Eicosanoids: These compounds, derived from eicosa (20-carbon) polyenoic fatty acids, comprise the prostanoids, leukotrienes (LTs), and lipoxins (LXs). 

Prostanoids include prostaglandins (PGs), prostacyclins (PGIs), and thromboxanes (TXs).
HARPERS ILLUSTRATED BIOCHEMISTRY30th ed, Page No:213