What are brownfields? 

A)  old landfill sites that have been replanted with vegetation 
B)  abandoned, once-contaminated industrial and commercial sites that have been cleaned up 
C)  forests that have been converted to new sanitary landfills 
D)  productive agricultural lands that use conservation tillage

Brownfields are abandoned or under-used industrial or commercial sites that are contaminated with pollutants or hazardous materials. They are typically located in urban areas and can be revitalized through cleanup and redevelopment efforts, which can boost economic growth and benefit local communities. Option A refers to the process of reclamation, Option C refers to the conversion of forested areas into sanitary landfills, and Option D refers to a sustainable farming practice.