Correct Answer - Option 2 : Methane
Methane (CH4):
It is a colorless, odorless, flammable gas used as a fuel to heat.
Elevated levels of methane can be found naturally in groundwater in some areas.
Methane in groundwater also may be the result of contamination caused by leaks from underground methane storage fields. Elevated level of methane released into water may lower oxygen levels and produce a fire or explosion.
