第30题: [单项选择]"Top soil" means ______. A. useless soil B. soil found under the earth C. soil on the surface of the earth D. dry soil which is found in the desert 参考答案:C 答案解析:依据第三段第二句“…preventing good and fertile top soil from being washed away…”……防止肥沃的上层土壤被大雨冲走。所以C是正确的。