What is the Bharat Stage $II$ equivalent to?

What is $BOD$?

Which one of the following is not an air pollutant?

Acid rain is caused by:

Delhi is one of the most polluted cities of the world. Which of the following steps were taken by the government to reduce vehicular pollution in Delhi?
$I.$ Phasing out of old vehicles
$II.$ Use of unleaded petrol
$III.$ Use of low sulphur petrol and diesel
$IV.$ Use of catalytic converters in vehicles
$V.$ Applying stringent pollution level norms for vehicles
$VI.$ Switch over of public transport from diesel/petrol to $CNG$
Which of the statements given above are correct?

What is the gradual increase in the concentration of toxicants at successive trophic levels called?