Question

A pan containing hot water is left on the counter and becomes cool mainly due to

Answer 1

It's B. Cold air penetrating hot water

Answer 2

C. heat from the water moving through the cooler air 

I think it's C because when something cools down, it has to reach a point of thermal equilibrium with the matter (in this case air) around it. So heat transfer happens through convection from the heat in the pan to the cooler surrounding air. The heated air becomes less dense and rises, while cooler air, sinks to the surface of the water, gets heated, and rises.This convection cycle keeps happening until the water in the pan is around the same temperature with the air around it.