Final answer:
Soybean oil is more susceptible to oxidative rancidity and flavor reversion because it contains a higher proportion of unsaturated fats compared to butter fat, coconut oil, and olive oil.
Step-by-step explanation:
The fat that would be more susceptible to flavor reversion due to oxidative rancidity is soybean oil. Oxidative rancidity occurs when fats are contaminated and undergo oxidation of unsaturated fatty acids, which leads to a bad odor and taste. Soybean oil, being high in unsaturated fats, is particularly prone to oxidation and hence flavor reversion. Butter fat and coconut oil are less susceptible since they contain higher amounts of saturated fats, which are more stable. Although olive oil contains antioxidants that provide some protection, it can also become rancid under certain conditions like exposure to light or metals.