- the layers of soil. More mature (older) soils have more of these layers fill in the blank please

I am not sure why your teacher isn't asking for the layers, but here is the list of layers;

A -(topsoil) Mostly minerals from parent material with organic matter incorporated. A good material for plants and other organisms to live.

E - (eluviated) - Leached of clay, minerals, and organic matter, leaving a concentration of sand and silt particles of quartz or other resistant materials – missing in some soils but often found in older soils and forest soils.

B - (subsoil) Rich in minerals that leached (moved down) from the A or E horizons and accumulated here.

C - (parent material) The deposit at Earth’s surface from which the soil developed.

R - (bedrock) A mass of rock such as granite, basalt, quartzite, limestone or sandstone that forms the parent material for some soils – if the bedrock is close enough to the surface to weather. This is not soil and is located under the C horizon.