`{:(,"Column A",,,"Column B"),(A.,"Defecation by living being","( )",a.,"Arsenic, mercury etc"),(B.,"Industrial operation","( )",b.,"Intesecticides, fungicides etc"),(C.,"Thermal pollution","( )",c.,"Amoeba, fungicides etc"),(D.,"Agricultural activities","( )",d.,"Favourable for growth of algae"):}`