单选题 Soil ______ is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions.

【正确答案】 C

【答案解析】[解析] 各项的意思是：preservation“维护，保护”；abrasion“磨损处，擦伤处”；erosion“(水，风等的)侵蚀，腐蚀”；eruption“爆发，喷发”；erupt into laughter“突然大笑”。