as alligators move from gator holes to nesting places, they help keep areas of open water free of invading vegetation.
위 문장 free of를 어떻게 해석해야하나요? not처럼 보면 되나요?agricultural pollution is a growing problem and industrial agriculture is forced by its character to treat the soil itself as a raw material, which it proceeds to use up.
위 문장에서 , which이하 문장 좀 이상한것같아서요 which 는 관계대명사인데 이하 문장이 완전해요,, 가리키는 선행사는 무엇인가요?