Answer: The tropical rainforest biome has four main characteristics: very high annual rainfall, high average temperatures, nutrient-poor soil, and high levels of biodiversity (species richness). Rainfall: The word “rainforest” implies that these are the some of the world's wettest ecosystems.
Explanation:
Separate Layer it's part of the "Atmosphere layers"
Well the big cities were by the river back then for importing goods by the boat
Arabs is most likely the answer. nor sure though