Based on how each food burned, which food would be the best to use for a fuel that has a steady flame and might burn for a long time? what was the composition of this food (which macromolecule was it mostly composed of)? how does this relate to the way that the human body utilizes this type of macromolecule as fuel?

Potato chip

Explanation:

There were studies about what is the lets say universal food, on which you would live the longest. Sorry, for not being able to find that source, but it stated that the two ingredients were potato and butter.

Now potato chips are mostly composed of carbs and fats. Therefore, it would take time to burn up, especially the fat, since it is being burnt down the longest.

So there you go. The answer is: potato chip

there is none because earth is stationary and flat.