Concept:Fertilizers that contain ammonium nitrogen can acidify the soil because the conversion of ammonium to nitrate releases hydrogen ions.Explanation:Sulphate of ammonia is (NH4)2SO4.When it is added to soil, it supplies ammonium ions (NH4+).Soil bacteria convert ammonium into nitrate through nitrification:NH4++2O2→NO3−+2H++H2OThe hydrogen ions (H+) released lower the soil pH.Repeated application of this fertilizer therefore makes the soil increasingly acidic.The other fertilizers listed do not acidify the soil as strongly or directly as sulphate of ammonia.Answer:B. sulphate of ammonia