Limit of $BOD$ prescribed by the Central Pollution Control Board $(CPCB)$ for the discharge of industrial and municipal wastewater into natural surface water is

Which of the following cannot be adulterated in petrol or diesel?

Catalytic converters:
$I.$ These are fitted into automobiles for reducing emission of poisonous gases like $NO_x$ and $CO$.
$II.$ They have expensive metals like platinum,palladium,and rhodium as catalysts.
$III.$ As the exhaust emission passes through the catalytic converter,nitric oxide splits into nitrogen and oxygen; carbon monoxide is oxidized to carbon dioxide,and unburnt hydrocarbons are burnt completely into $CO_2$ and $H_2O$.
$IV.$ Motor vehicles fitted with catalytic converters should use unleaded petrol because lead in the petrol inactivates the catalyst.
Which of the statements given above are correct about catalytic converters?

$A$ : $ESP$ can remove particulate matter by more than $99\;\%$.
$R$ : Anode attracts the particles and provides a positive charge to them,allowing them to fall.

What is removed by the scrubber method in a chemical factory?

In eutrophication,dissolved $O_2$ ....... and $BOD$ ......