Which of the following best describes topsoil?
A.
Topsoil is made entirely of decomposed organic remains.

B.
Topsoil is made of humus and clay minerals washed down from the layer above the topsoil.

C.
Topsoil is made of humus and mineral particles weathered from the soil's parent material.

D.
Topsoil is made entirely of minerals weathered from the underlying parent material.