The effect of pollution is first marked on:

The concentration of a pesticide required to destroy $50\%$ of a pest population is called:

Decrease in the rate of mitosis in root tips is caused by

What is $BOD$?

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?

To which class of pesticides do $DDT$,$BHC$,aldrin,and endosulphan belong?