Which one of the following statement is not true?

• A

  Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant.

• B

  pH of drinking water should be between 5-5 and 9.5.

• C

  Concentration of DO below 6 ppm is good for the growth of fish.

• D

  Clean water would have a BOD value of less than 5 ppm.