  We compare two competing conjectures of the color confinement in QCD, the
monopole condensation and the Abelian dominance, and show that it is the
monopole condensation which is responsible for the confinement. To demonstrate
this we present a new gauge invariant integral expression of the one-loop QCD
effective action which has no infra-red divergence. With this we show that,
just as the GSO-projection restores the supersymmetry and modular invariance in
NSR string theory, the color reflection invariance ("the C-projection") assures
the gauge invariance and the stability of the monopole condensation. This
establishes the monopole dominance in QCD. In doing so we point out critical
defects in the calculation of the Savvidy-Nielsen-Olesen (SNO) effective
action.
