Answer:
The answer is letter A: density.
Explanation:
On the bedrock, these materials lay with different arrangements within the sandstone because they have different densities. The natural gas is on top because of its low density, gases are a homogeneous fluid of low density and low viscosity. Followed by the oil, that has larger molecule components and heavier components, making them denser than gas. Next is the water, which has the most density of all (due to its molecules that can pack tightly together), so it comes in last.