Final answer:
The topsoil in a soil profile is considered the A horizon, while the subsoil is considered the B horizon.
Step-by-step explanation:
The topsoil in a soil profile is considered the A horizon, while the subsoil is considered the B horizon. The A horizon is typically darkly colored due to the presence of organic matter, and it consists of a mixture of organic material with inorganic products of weathering. The subsoil, or B horizon, is an accumulation of mostly fine material that has moved downward, resulting in a dense layer in the soil.