Q. Pick up the correct statement from the following?
a. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
b. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
c. Solubility of oxygen in sewage is 95% of that of distilled water
d. All the above
No explanation is available for this question!
