Relation between C/O, O/H and stellar mass. Left panel: C/O–O/H relation. Our sample is color-coded by Σ_SFR. The symbols with cyan edges are galaxies with limits in OIII]λ1666. We compare our results with local BCD galaxies (small green circles; Garnett et al. 1995, 1997; Kobulnicky et al. 1997; Kobulnicky & Skillman 1998; Izotov et al. 1999; Thuan et al. 1999; Berg et al. 2016; Senchyna et al. 2021) and HII regions (small blue squares; Garnett et al. 1995, 1999; Kurt et al. 1995; Mattsson 2010; Senchyna et al. 2021). We also show chemical evolution models from the literature as dashed lines with the colors described in the legend (Garnett et al. 1995; Mattsson 2010; Nicholls et al. 2017). The dashed magenta line is the scaled N/O-mass relation in Andrews & Martini (2013) assuming the constant C/N factor based on Berg et al. (2019). The shaded magenta region is the 1σ uncertainty considering the observed scatter in the relation and the conversion factor. Right panel: Relation between C/O and stellar mass. The symbols are the same as in the left panel. In this panel, the dashed black line is the relation presented in Llerena et al. (2022) at z ∼ 3 based on stacking.