Correct option is D
Bioremediation refers to the use of living organisms—mainly microorganisms—to degrade environmental contaminants into less harmful forms. The correct match between the terms in Column X and their definitions in Column Y is as follows:
Bioventing involves supplying air (oxygen) to unsaturated soils to stimulate the biological degradation of contaminants by indigenous microorganisms under aerobic conditions.
Natural attenuation is the natural reduction in contaminant concentrations through processes like biodegradation, dispersion, dilution, volatilization, and chemical reactions without human intervention.
Air sparging introduces air directly into saturated zones (below the water table) to enhance the volatilization and biodegradation of pollutants.
Biostimulation improves the natural biodegradation process by adding nutrients (like nitrogen and phosphorus) to encourage microbial growth.
Hence, the correct answer is: (1) A (iii), B (i), C (ii), D (iv)
