Biochemical oxygen demand values of our water samples A,B,C and D are respectively 50 ppm, 100 ppm, 150 ppm and 40 ppm. Arrange them in the descending order of their purity.

Biochemical oxygen demand values of our water samples A,B,C and D are

1.	Biochemical oxygen demand values of our water samples A,B,C and D are respectively 50 ppm, 100 ppm, 150 ppm and 40 ppm. Arrange them in the descending order of their purity.
Answer» Solution :More the BOD value, more the extent of pollution and LESS the purity of water. Thus purity of water SAMPLES is in the order `D GT A gt B gt C`