If a cup of coffee is at 90°C, how will heat flow when someone with a body temperature of 36°C touches it?

When considering the scenario where a cup of coffee is at 90°C and is touched by a person with a body temperature of 36°C, heat transfer will occur based on the principle of thermal energy flow, which is always from the warmer object to the cooler one.

In this case, the cup of coffee is significantly hotter than the person's hand. Therefore, the thermal energy will flow from the coffee to the hand until thermal equilibrium is reached, meaning the hand heats up while the coffee loses some of its heat. This is why the correct answer is that heat flows from the cup to the hand.

Heat transfer occurs through conduction in this context, as the two surfaces of the coffee cup and the hand are in direct contact, allowing energy to transfer efficiently between them. The surrounding air will experience minimal effect from this direct contact in terms of immediate heat flow, making the other options less relevant to the primary interaction taking place.