TOEFL Reading: ETS-TOEFL阅读机经 - 7GWW145L1450I_OAL$

According to paragraph 7, soil on steep slopes tends to remain poorly developed because A. soilon steep slopes tends to be very acidic B. soil that forms on steep slopes tends to be heavy in texture C. so much of the soil that forms on steep slopes becomes eroded quickly D. soil differentiates very quickly from parent materials