TOEFL Reading: ETS-TOEFL阅读机经 - 8LW68UBP4575U16JL$

Paragraph 6 supports which of the following ideas about organic material soil? A. Most of the organic material in soil comes from fibrous root systems. B. How organic material is distributed in soil depends on the type of vegetation the soil supports. C. The organic materials in soil prevent acids from forming during the weathering process. D. Animals, bacteria, and fungi consume much of the nutrient content in soil.