Final answer:
The major factor that determines how slowly a food cools is the temperature difference between the food and its environment, which is the primary driver of the rate of heat transfer.
Step-by-step explanation:
The major factor that determines how slowly a food cools is d) Temperature difference. This refers to the difference between the temperature of the food and the surrounding environment. According to the principles of thermodynamics, heat transfer occurs more rapidly when there is a large temperature difference and slows as the difference decreases. As the food approaches room temperature, the rate of cooling decreases.
The other options, such as room temperature, air pressure, and volume of food, can also affect cooling rates, but the temperature difference is the primary driver. For instance, a larger volume of food will take longer to cool simply because there is more of it to cool down, but even in this case, the rate of cooling, at any moment, depends on the current temperature difference.
Heat capacity, like that of ice, affecting how much energy is absorbed during state changes, is another facet of cooling, but still within the concept of temperature difference impact on energy exchange.