Explain which of the three compounds has a mass spectrum which contains peaks at \(m{\text{/}}z = 59\) and 44.

methyl ethanoate;

peak at 44 corresponds to loss of two methyl/CH₃ groups (and peak at 59 the loss of the first) / the only isomer with two methyl groups / OWTTE;

Many students could use the spectroscopic data provided to correctly identify the compounds, with the first part of the question, dealing with mass spectrometer data, probably proving the most challenging.