Carbon-to-oxygen (upper panel) and nitrogen-to-oxygen (lower panel) as functions of [O/H] in the solar neighbourhood. Data (symbols) are the same as in Fig. 3. Also shown are the predictions from Models 1 (short-dashed lines) and 2 (solid lines). The two models differ only in the adopted location of the mass cut in models of SNII explosions. See the electronic edition of the journal for a colour version of this figure.