Four samples of water A. B, C and D have the D.O. levels of 4 ppm. 3.8 ppm, 2.1 ppm and 4.9 ppm respectively 1he most polluted sample of water is

Four samples of water A. B, C and D have the D.O. levels of 4 ppm. 3.8

1.	Four samples of water A. B, C and D have the D.O. levels of 4 ppm. 3.8 ppm, 2.1 ppm and 4.9 ppm respectively 1he most polluted sample of water is
Answer» D B C A Answer :C