You will get 8 points:
1)how does the c horizon form?
2)a geoligist is studying a layer of soil in the sahara. the soil layer contains little humus but a lot of clay and other rock particles. which soil layer is it?

C horizon formation :
it is the unconsolidated material present beneath B horizon ..
when large soil particles and rocks break during the weathering of R horizon then it is formed but in dry regions gypsum and carbonates also get accumulated ..
2)
it is the B horizon present beneath A , O or E horizon ..it commonly accumulates clays .iron and different oxides .. also the other name of it is subsoil :)