$BOD$ stands for:

Catalytic converters are fitted into automobiles to reduce the emission of poisonous gases. These converters use expensive metals as catalysts,which are:

Oil slick causes mass scale death of fishes due to

$A$ lake with an inflow of domestic sewage rich in organic waste may result in:

'Bad' ozone is formed in

Discuss briefly the following:
$(a)$ Greenhouse gases
$(b)$ Catalytic converter
$(c)$ Ultraviolet $B$