The correct option is B 1:2
The balanced chemical reaction for both the reactions are:
CH4+2O2→CO2+2H2OC2H6+72O2→2CO2+3H2O
Applying Gay lussac's Law,
1 L of CH4 requires 2 L of O2 at STP.
1 L of C2H6 requires 72 L of O2 at STP.
Let a and b litres of CH4 and C2H6 present respectively.
So,
a L of CH4 requires 2a L of O2 at STP.
b L of C2H6 requires 72 b L of O2 at STP.
Therefore,
a+b=32a+7b2=9
On Solving,
a=1 L
b=2 L
Mole ratio of CH4:C2H6 =1:2