Similar to the Campeonato Brasileiro, teams inside the lower series, including B and C, is often promoted to the very best division every year. In the case of Italy, only the top a few groups in Serie B are promoted to Serie A (in Brazil, advertising happens for 4 groups https://konhcitv05789.ageeksblog.com/36274231/the-smart-trick-of-what-is-serie-a-that-nobody-is-discussing