Hummus is an important component of healthy soil. how does hummus form?

Humus (hummus) is a dark organic matter in the soil which is produced by the decay of leaves or twigs (leaf litter). The litter is decayed in the soil by the action of microbial communities and chemcial reactions (together called as biogeochemical reactions). This process is also known as decomposition. The higher humus content in the soil makes it more fertile because there are more nutrients releasing due to increased turnover of the decomposing bacteria. Further, humus formation is increased if more water (moisture content) and oxygen is available.

prism b but im not for sure