It would be the topsoil because Soil is usually layered. The uppermost layer is called topsoil and this layer contains humus, plant roots, and living creatures. The more humus found in topsoil, the more nutrient rich the topsoil and the better the conditions for growing plants. The middle layer is called subsoil.
Gravity is when you drop something, but in this case you aren’t dropping the ball. It definitely isn’t chemistry because you aren’t changing molecules or anything so that only leaves A which is the most reasonable answer anyways.
