The answer is I. 25 meters.
I belive it it O because <span>An O horizon has at least 20% </span>organic matter<span> by mass. Two main scenarios result in the formation of an O horizon: saturated, </span>anaerobic<span> conditions (wetlands) or high production of leaf litter in forested areas. Anaerobic conditions slow the </span>decomposition<span> process and allow organic material to accumulate. An O horizon can have various stages of decomposed organic matter: highly decomposed, sapric; moderately decomposed, hemic; and minimally decomposed, fibric. In a fibric O layer, plant matter is recognizable (e.g., it is possible to identify a leaf). Sapric material is broken down into much finer matter and is unrecognizable as a plant part. Hemic is in between sapric and fibric, with some barely recognizable plant material present. It is possible to have multiple O horizons stacked upon one another exhibiting different decomposition stages. Because of their organic content, these horizons are typically black or dark brown in color. The dominant processes of the O horizon are </span>additions<span> of organic matter, and </span><span>transformations </span><span>from fibric to sapric
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B. It encouraged exploration for a new trade route
Ganges for sure but idk about irrawaddy the mesopotamian ones
