@chemistry?

The corresponding equations are :
C₂H₆ + 3.5O₂ → 2CO₂ + 3H₂O
C₂H₄O₂ + 2O₂ → 2CO₂ + 2H₂O
C₂H₆O + 3O₂ → 2CO₂ + 3H₂O
C₃H₆O + 4O₂ → 3CO₂ + 3H₂O

Refer to the coefficient of the above equation. When 1 mole of C₂H₆, C₂H₄O₂, C₂H₆O and C₃H₆O are burnt, 3.5 moles, 2 moles, 3 moles and 4 moles of oxygen are consumed respectively. C₃H₆O will consume the greatest amount of oxygen.

The answer: C₃H₆O

The products of combustion are CO2 and H2O

C2H6 will produce 2mol CO2 and 3mol H2O
Oxygen consumed = 2mol O2 + 1.5 mol O2 = 3.5 mol O2

C2H4O2 will produce 2mol CO2 and 2mol H2O
Oxygen consumed = 2mol O2 + 1mol O2 - 1mol O2 in molecule = 2 mol O2

C2H6O will produce 2mol CO2 and 3 mol H2O
Oxygen consumed = 2 mol O2 + 1.5 mol O2 - 0.5 mol O2 in molecule = 3 mol O2

C3H6O will produce 3 mol CO2 + 3mol H2O
Oxygen consumed = 3 mol O2 + 1.5 mol O2 - 0.5 mol O2 in molecule = 4 mol O2

C3H6O consumes the greater amount of O2