3. Which of the horizons in the soil profile shown represent the organic material? C. horizon A ( topsoil) A. horizon O (humus) D. horizon C(parent rock B. horizon B (subsoil) 4. In which horizon do most animals such as bugs live? D. topsoil C. bedrock A. humus B. subsoil 5. The horizon that contains partly weathered rock. C. A horizon (topsoil) A. Chorizon (parent rock) D. bedrock B. B horizon (subsoil) 6. What is soil horizon? A. a factor influencing how soil is formed B. an organism found within the soil C. a technique used to map soils D. a layer of soil 7. Why is organic matter (humus) an important part of soil? It A. helps improve water infiltration B. can break down organic pollutants. C. converts nitrogen in the air into the nitrates used by plants. D. is rich in nutrients, which is important for fertility. 8. Which animals would best help the soil hold water? A. earthworm making holes under the surface B. horse making trenches when they gallop C. cattle making depressions with their hooves D. sheep pulling up plants by their roots 9. Why are the top layers of soil darker in color than the lower layers? A. they contain less organic matter C. they contain more organic matter D. the pore space B. the parent rock 10. The organic material in soil is_ D. humus C. fertilizer B. feldspar A. bedrock​