Which of the Following Relies Upon Existing Biodiversity for the Decontamination

Which of the following relies upon existing biodiversity for the decontamination of polluted ecosystems?

A) Some types of bacteria naturally convert toxins to less hazardous forms.
B) Sawdust from lumber mills can be used to soak up chemicals that have saturated natural ecosystems.
C) Species in contaminated areas may evolve into forms that can survive in contaminated soils.
D) After centuries of agricultural production, soils depleted of nitrogen can be replenished by promoting the growth of nitrogen-fixing organisms.