Notes. The number of retained O-B2 stars and H II regions after each analysing step mentioned in Sect. 3.1. “Step-1” identified O-B2 stars that fall within the angular radii of H II regions. “Step-2” was to select O-B2 stars located within the newly defined boundaries of H II regions. “Step-3” checked the parallax consistency of the stars within the boundaries of H II regions and the parallax uncertainties of stars. "Step-4" excluded the potential foreground or background stars whose parallaxes do not fall within 3σ of that of the majority member stars.