The Absence of a Layered Structure in the Soil Pictured

The absence of a layered structure in the soil pictured below occurs because

A) leaching is so strong that it removes the distinguishing features of each layer.
B) swelling as the soil absorbs water and shrinking as it dries out removes the horizonation.
C) calcification has caused caliche to be left behind in all of the horizons.
D) volcanic ash has penetrated very deeply beneath the surface in this soil type.