(A)Pb>50ppm → Lead toxicity causes liver and kidney damage, neurological disorders, etc. So, (A) → (IV) Liver damage (B)SO4‌2−>500ppm → High sulfate content in water has a laxative effect. So, (B) → (III) Laxative effect (C)NO3−>50ppm → High nitrate levels cause methemoglobinemia ('Blue baby' syndrome) in infants. So, (C) → (II) 'Blue baby' syndrome (D)F−>2ppm → Excess fluoride causes fluorosis → brown mottling of teeth. So, (D) → (I) Brown mottling of teeth Correct matching: A-IV, B-III, C-II, D-I
