  Stars in the mass range ~8 - 12 $M_{\odot }$ are the most numerous massive
stars. This mass range is critical because it may lead to supernova (SN)
explosion, so it is important for the production of heavy elements and the
chemical evolution of the galaxy. We investigate the critical transition mass
($M_{up}$), which is the minimum initial stellar mass that attains the
conditions for hydrostatic carbon burning. Stars of masses < $M_{up}$ evolve to
the Asymptotic Giant Branch and then develop CO White Dwarfs, while stars of
masses $\geqslant $ $M_{up}$ ignite carbon in a partially degenerate CO core
and form electron degenerate ONe cores. These stars evolve to the Super AGB
(SAGB) phase and either become progenitors of ONe White Dwarfs or eventually
explode as electron-capture SN (EC-SN). We study the sensitivity of $M_{up}$ to
the C-burning reaction rate and to the treatment of convective mixing. In
particular, we show the effect of a recent determination of the $^{12}C+$
$^{12}C$ fusion rate, as well as the extension of the convective core during
hydrogen and helium burning on $M_{up}$ in solar metallicity stars. We choose
the 9$M_{\odot }$ model to show the detailed characteristics of the evolution
with the new C-burning rate.
