Radius of a ﹩3.2\,{M}_{\odot }﹩ star as a function of its age. The stellar models we study in its evolutionary track are labeled with solid dots and circles. Seven major evolutionary phases, which are the same as those shown in Figure 1, are labeled here. Absent of significant angular momentum loss, this star cannot initiate mass transfer during those phases of its evolution when its radius is smaller than during a preceding phase of evolution (thin dotted line, e.g., during core helium burning, or just beyond the point labeled TMS). We refer to these forbidden evolutionary phases as “shadowed.” For reviewing clearly the rapid evolution in advantage phases, a break is made in the horizontal axis, and the axis spacing is reduced by half.