Transitions of lactaldehyde, CH₃CH(OH)C(O)H, identified toward G+0.693 (see text; listed in Table A.5). The red line shows the best LTE fit of CH₃CH(OH)C(O)H, while the blue line represents the combined emission of all molecules identified in the survey, including CH₃CH(OH)C(O)H (observed spectra are shown as gray histograms). The quantum numbers for each transition are shown at the bottom of each panel. For panels with multiple lines, we show the quantum number of the lowest-frequency transition. The transitions are sorted by increasing frequency. The molecular structure of CH₃CH(OH)C(O)H is also shown (C atoms in gray, O atoms in red, and H atoms in white).