Q.Choose the correct option.
Oxidative Rancidity is ______ reaction
a. addition b. subtitution c. Free radical d. combination

Rancidity is the unpleasant smell and taste that develops in stored oils and fats, and it has two distinct chemical causes. Hydrolytic rancidity happens when water, often with microbial/enzyme catalysis, hydrolyses the ester bonds of a triglyceride (Triglyceride + 3 H2O -> Glycerol + 3 free fatty acids); the specific fatty acids released determine the specific off-flavour -- short-chain butanoic/hexanoic/octanoic acids in rancid milk and butter, palmitic/stearic/oleic acids in rancid chocolate, and lauric acid giving coconut oil a soapy flavour. Oxidative rancidity, the second cause, happens when atmospheric oxygen attacks the C=C double bonds of unsaturated fatty acids in a free-radical chain reaction (initiated by light as photo-oxidation, or catalysed by enzymes/metal ions), breaking the fat down into small, volatile aldehydes and carboxylic acids that carry the characteristic rancid taste; more double bonds (polyunsaturation) and higher temperature both speed this process up.