If we continuously add sewage water into a river,the $BOD$ of the river will:

Cyanosis is caused by

Differentiate between wet deposition and dry deposition.

Why is $CNG$ considered a better fuel than diesel/petrol?
$I.$ $CNG$ burns most efficiently without leaving any unburnt remnant behind.
$II.$ $CNG$ is cheaper than petrol or diesel.
$III.$ $CNG$ cannot be siphoned off by thieves and adulterated like petrol or diesel.
Which of the statements given above are correct?

Euro-$III$ norms stipulate that sulphur be controlled at ....... $PPM$ in diesel and $PPM$ in petrol.

In an area where $DDT$ had been used extensively,the population of birds declined significantly because