Beware: one of the equations is balanced wrong.
You are most likely expected to base your decision on how many liters of CO
2 are produced per 1L of gaseous fuel.
But this question is wrong on at least two levels
First: you can't store acetylene just a as a compressed gas. Second: to find which of the fuels is better you should look not at the amount of carbon dioxide produced by burning 1L of fuel, but compare amount of CO
2 produced for cooking a meal (or just boiling a water, to make things easier). That requires going behind just molar ratios and comparing enthalpies of combustion. I understand this is probably beyond what you know now, but I hate it when questions are based on misconceptions and/or wrong assumptions.