Combustion O2 requirement from balanced equation Steps:

• General combustion: C_xH_yO_z + O2 → CO2 + H2O; balance atoms to find O2 coefficient.
• A. CH3OH: CH3OH + 1.5 O2 → CO2 + 2 H2O (1.5 mol O2 needed).
• B. C2H5OH: C2H5OH + 3 O2 → 2 CO2 + 3 H2O (3 mol O2 needed).
• C. CH3CHO: CH3CHO + 2 O2 → 2 CO2 + 2 H2O (2 mol O2 needed).

Why C is correct:

• CH3CHO (C2H4O) combustion equation balances with exactly 2 mol O2 per mol compound, per standard organic chemistry balancing.

Why the others are wrong:

• A requires 1.5 mol O2, not 2.
• B requires 3 mol O2, not 2.
• D: Not enough information.

Final answer: C