Queena Ramadhani Early, “Maximizing Return with Minimal Risk: A Comparative Study of Optimal Portfolios Using Single Index Model and Markowitz Model (Study on Companies Included in The IDX LQ45 Low Carbon Leaders Index for the Years 2022-2024)” Thesis D4 Accounting Department Poiliteknik Negeri Semarang, under the guidance of Muhammad Rois, S.E., M.Sc. And Prihatiningsih, S.E., M.M. De…