Which of the following pairs is mismatched?

When did the worst environmental nuclear power plant accident and the $MIC$ gas tragedy occur,respectively?

Soil conservation can be best achieved by having

Match the columns :

Column - $I$	Column - $II$
$(1)$ Nitrous oxide	$(a)$ Secondary pollutant from car exhaust.
$(2)$ Chlorofluorocarbons	$(b)$ Combustion of fossil fuels,wood etc.
$(3)$ Methane	$(c)$ Denitrification
$(4)$ Ozone	$(d)$ Refrigerators,aerosols,sprays
$(5)$ Carbon dioxide	$(e)$ Cattle,rice fields,toilets

Consider the following statements about Ramesh Chandra Dagar's work in the field of organic farming:
$I.$ Ramesh Chandra Dagar's work includes bee-keeping,dairy management,water harvesting,composting,and agriculture in a chain of processes.
$II.$ In this process,there is no need to use chemical fertilisers for crops as cattle excreta is used as manure.
$III.$ Crop waste is used for making compost,which is used as natural fertilizer.
$IV.$ Compost generates natural gas,which is used for the energy needs of the farm.
Which of the statements given above are correct?

Assertion : Methane,a component of greenhouse gases,contributes about $20$ percent to global warming.
Reason : The introduction of multi-point fuel injection engines in automobiles has decreased methane content in the exhausts.