question_answer 40)

  Top soil contains the following (a) Humus and living organisms only                        (b) Humus and soil particles only (c) Humus, living organisms and plants                   (d) Humus, living organisms and soil particles

Answer:

  (d) The term soil profile is the vertical section of earth's crust, which is made up of a succession of horizontal layers also called as horizons, each of which varies in thickness, colour, texture, structure, consistency, porosity, acidity and composition. The upper or A-horizon is the top soil which contains most of the litter living organisms and humus. It also has a zone of leaching, through which dissolved materials weep downward. The roots of small plants are embedded in top soil. The second or B-horizon is composed of the mineral soil (sub soil). The third or C-horizon contains the unconsolidated parent material. The last or D-horizon comprises of rock or unmodified parent material.