Packets of potato chips are usually flushed with which one of the following gases to prevent rancidity?

Option 3 : Nitrogen

The correct option is Nitrogen.
CONCEPT:
Rancidity

• Rancidity, condition produced by aerial oxidation of unsaturated fat present in foods and other products which gives unpleasant odor or flavor.
• When a fatty substance is exposed to air, its unsaturated components are converted into hydroperoxides, which break down into volatile aldehydes, esters, alcohols, ketones, and hydrocarbons.
• This gives out bad smell.

EXPLANATION:

• Nitrogen gas is used during the packaging process to exclude and remove air and prevent oxidation. 
• Oxygen is highly-reactive and it combines with other molecules, which results in food spoiling or losing its' freshness.