Permanent hardness of water can be removed by adding
-
chlorine
-
washing soda
-
potassium permanganate
-
bleaching powder
B
Correct answer
Explanation
Permanent hardness is caused by dissolved calcium and magnesium sulfates/chlorides that can't be removed by boiling. Washing soda (sodium carbonate) softens water by precipitating these ions as insoluble carbonates. Chlorine and bleaching powder are disinfectants, while potassium permanganate is an oxidizing agent - none remove hardness.