The relation between stellar mass and K_S absolute magnitude of Class II sources. The black dots represent the Robitaille et al. (2006) Stage 2 models with 0.001 < M_disk/M_* < 0.01, 0.08 < M_* < 7 M_⊙, and 30^° < inclination angle < 60^°. The red curve shows the robust polynomial fitting while the gray region shows the 1σ uncertainty of the fitting. The CTTS in L1641 from Fang et al. (2013) are marked with green filled circles. Most of CTTS are located in the gray region, which confirms that this M_KS − M_* relation for Class II sources is consistent with the observational results.