The 'Itai-itai' disease is caused by the poisoning of which of the following?

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?

Which of the following statements is correct?

Which one of the following statements regarding $BOD$ is true?

If the concentration of lead in the blood reaches ........,it is considered a warning sign.

Which component of a living cell is affected by the pollutant $SO_2$?