Which one of the following gases is most significant as air pollutant ?

A. Velocity of flow
B. Diameter of the sewer
C. Discharge
D. All the above

A. 100 cm
B. 90 cm
C. 80 cm
D. 50 cm

A. 2.25
B. 2.50
C. 2.55
D. 2.65

A. 5 – 10 years
B. 15 – 20 years
C. 30 – 40 years
D. 40 – 50 years