Assertion: The concentration of methane in the atmosphere has more than doubled in the last 250 years.
Reason: Wetlands and rice fields are the major sources of methane.

If both assertion and reason are true and reason is the correct explanation of assertion

If both assertion and reason are true but reason is not the correct explanation of assertion

If assertion is true but reason is false

If both assertion and reason are false.

Solution

If both assertion and reason are true and reason is the correct explanation of assertion

Hydrocarbon are major air pollutants. Methane is produced naturally during decomposition of organic matter, incomplete biomass combustion. Its concentration was 700 ppb in pre-industrial times and 1750 ppb in 2000. So the concentration has more than doubled in the last 250 years. Flooded paddy fields, marshes, cattles etc. are the major sources of this gas.