The major source of noise pollution,worldwide,is due to:

Compared to normal water,the $BOD$ of sewage-polluted water is . . . . . . .

The most hazardous metal pollutant used in automobiles is .....

The highest $DDT$ concentration in an aquatic food chain shall occur in:

Acid rain is primarily caused by which of the following pollutants?

Nitrogen oxides are produced from the emissions of automobiles and power stations,which are a source of fine particulate matter in the air,leading to the formation of .....