Answer:
The correct answer would be humus.
Humus is the organic material of the soil formed by the decomposition of the dead plants and animals. It is thick and dark in color (brown or black) and can also be produced by the process of composting.
It is very for the soil as it adds moisture to the soil, enhances the structure of the soil which increases the aeration and drainage.
It favors the growth of organisms (such as earthworm) helpful for the growth of plants and adds lots of nutrients to the soil, specially nitrogen.
In contrast, loam is a type of soil which is composed of silt, sand, and clay in 40-40-20 ratio. Regolith referred to the superficial layer covering the solid rocks or bedrock. It is formed by the accumulation of soil, dust, broken rocks etc on the bedrock.
Lastly, talus referred to the slope which is formed by deposition of shattered rock debris at the base of a cliff.
