Noise level heard inside a bus in busy city traffic or inside a sub-way train corresponds to about ______________ decibels?

A. Dissolved oxygen content
B. Biological oxygen demand
C. Vapor pressure
D. All A., B. and C.

A. Silica gel
B. Active carbon
C. Bog iron
D. Limestone powder

A. Dilution with inert material
B. Discharging to atmosphere through tall stacks after dilution
C. Disposing off in rivers & oceans
D. Filling in steel crates and shooting it off out of earth’s gravity

A. Colloids or aerosols
B. Powder
C. Dust
D. Smoke

A. Cancer
B. Bronchitis
C. Asphyxiation
D. Corrosion

A. Automobile exhaust
B. Forest fire
C. Bacterial action in soil and swamp areas
D. All A., B. and C.