Identify the structure that is consistent with the following data set: molecular formula: C₉H₁₀O₂, IR absorption at 1669 cm-1?
a) Ethanol (CH₃CH₂OH)
b) Acetone (CH₃COCH₃)
c) Benzoic acid (C₆H₅COOH)
d) Butanoic acid (CH₃CH₂CH₂COOH)