Which contains the greatest mass of oxygen: (2.0) mol of formaldehyde ((CH₂O)), (1.5) mol of methanol ((CH₃OH)), or (1.2) mol of acetic acid ((CH₃CO₂H))?

a. (2.0) mol of formaldehyde ((CH₂O))
b. (1.5) mol of methanol ((CH₃OH))
c. (1.2) mol of acetic acid ((CH₃CO₂H))
d. All contain the same mass of oxygen.