Isolated JWST/MIRI-MRS spectrum between 6.8 and 8.8 μm of IRAS 2A (Rocha et al. 2024) and B1-c (top panel), along with the best-fit decomposition of the B1-c spectrum (bottom panel). The IRAS 2A spectrum was binned by a factor of four, and therefore shows a lower spectral resolution. The B1-c spectrum is the version after removing the gas-phase lines (i.e., the black line in Fig. 3d). In the bottom panel, nine out of 12 candidate species that have statistically significant contribution to the 6.8–8.8 μm range are displayed, with the other three species (SO₂, CH₃COOH, and CH₃CN) excluded. The best-fit mixing conditions (constituents, ratio, and temperature) selected in Sect. 3.2.5 are labeled in the legend. The residue is shown below. A step-by-step version of the best-fit results of the B1-c spectrum is given by Fig. K.1¹.