Final answer:
Polyunsaturated fats are the most unstable and least resistant to rancidity due to their multiple double bonds, which make them more prone to oxidation compared to saturated and monounsaturated fats.
Step-by-step explanation:
The fatty acid that would be the most unstable or least resistant to rancidity is C) Polyunsaturated Fat. These fats contain multiple double bonds which are points of unsaturation. Due to the presence of several C=C double bonds, polyunsaturated fats such as canola oil and omega-3 fatty acids like alpha-linolenic acid, are more prone to oxidation and rancidity compared to their saturated and monounsaturated counterparts. Unsaturated fats and trans fats both have double bonds, but the configuration (cis vs. trans) affects their stability and physical states at room temperature. Saturated fats do not have double bonds, making them more stable and typically solid at room temperature.