'Heat islands' are produced due to

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?

Give differences: $BOD$ and $COD$.

Which of the following gases does not cause acid rain?

Nitrogen oxides produced from the emission of automobiles and power plants are the source of fine airborne particles which lead to:

Assertion: $A$ suspended particulate matter $(SPM)$ is an important pollutant released by diesel vehicles.
Reason: Catalytic converters greatly reduce pollution caused by automobiles.