Final answer:
The distinguishing characteristics of mollisols come from their organic-rich topsoil, which is highly fertile and supports agriculture in temperate climates.
Step-by-step explanation:
The strongest distinguishing characteristics of mollisols are derived from their thick, dark, organic-rich topsoil known as the A-horizon or mollic epipedon, which forms under grassland vegetation. These soils are notable for their high fertility and are typically found in areas with moderate temperatures and rainfall, making them excellent agricultural soils. The rich organic content of mollisols is a result of the decomposition of grass roots and other organic materials, which provide a significant amount of nutrients such as nitrogen and phosphorus, essential for plant growth.