Best fit of the observed spectrum of G19.88-0.53 in a line-rich frequency range (259.4–260.6 GHz). The black and colorful spectra correspond to the observed spectrum and the modeled spectra of each species, respectively. Only the O-bearing COMs targeted in this paper (excluding CH₃OH) are shown here. Two strong lines of methanol are labeled in gray text in the panels. The same figure but for the full upper tuning is given in Fig. A.5.