A. The products have a lower potential energy than the reactants.
We know this because of the discovery of fossils and bones. We can find out roughly when they existed because of carbon dating.
A) Salt, because salt can easily dissolve in water. Oil would not dissolve or evaporate in water (think of an oil spill - does that oil dissappear?). Aluminum foil would definitely not dissolve in water, so it is not soluble.
C. heat tends to balance out and it must travel to cooler areas to balance out the temp