Much like the Campeonato Brasileiro, groups during the lower series, like B and C, is often promoted to the top division yearly. In the case of Italy, only the major 3 groups in Serie B are promoted to Serie A (in Brazil, advertising transpires for 4 teams in Serie B). https://k-o-nh-c-i-527058.wizzardsblog.com/37594199/the-smart-trick-of-what-is-serie-a-that-nobody-is-discussing