The paper contains a self-contained alternative proof of my Theorem in Characterization of generic extensions of models of set theory, Fund. Math. 83 (1973), 35–46, saying that for models $M\subseteq N$ of ZFC with same ordinals, the condition $Ap{r}_{M,N}\left(\kappa \right)$ implies that $N$ is a $\kappa$-C.C. generic extension of $M$.