The mass-metallicity relation as predicted by our best models. The total infalling masses range from M_inf = 10⁸ to 10¹⁰ M_⊙, and the more massive one prefers a longer burst duration. The results with different numbers of burst are shown in different lines, solid red, dash-dotted black, long-dashed magenta, and short-dashed blue lines are for n = 3,5,7,9, respectively. The observational data of BCDs (open cyan circles) and dIrrs (open cyan triangles) are the same as in Fig. 1.