Plots of the evolution and correlation of the derived physical parameters. ν_t vs. N_Ly (upper-left), EM vs. N_Ly (upper-right), n_e vs. N_Ly (bottom-left), and diam vs. N_Ly (bottom-right) for HC H II regions (red dots), intermediate objects between HC H II region and UC H II regions (blue), UC H II regions in this work (green dots), and CORNISH UC H II regions (gray dots). The CORNISH UC H II regions sample refers to the whole CORNISH UC H II regions sample from Kalcheva et al. (2018) by excluding UC H II regions in this work. The magenta arrow indicates the evolutionary trend of the physical properties.