[O/Fe] ratios in GAEA realization. The blue lines refer to the predictions of the CR-IGIMF, and the shaded area corresponds to the 15−85th percentiles. As reference, the dashed black lines show predictions from the HDLF16 model. Only model ETGs (i.e., B/T > 0.7) were considered. The observational constraints are taken from Thomas et al. (2010, contours), Arrigoni et al. (2010, dark gray circles), Spolaor et al. (2010, light gray squares).