= Solution
Starting from a matter-antimatter symmetric ensemble, exact <charge conjugation> would pair every baryon-producing process with an equally probable antibaryon-producing process. Their contributions to the net <baryon number> cancel. Thus <C violation> is necessary. Violating <charge conjugation> alone is insufficient: if <CP symmetry> is exact, the parity-reflected conjugate channels still have equal probabilities and cancel in a <CP symmetry> invariant ensemble. One needs <CP violation> as well.
The remaining <Sakharov conditions> are \b[<baryon number> violation and departure from <thermal equilibrium>]. Conserving <baryon number> cannot turn an initially zero value into a nonzero one. In <thermal equilibrium>, under the usual <CPT theorem> hypotheses and with no imposed <chemical potentials> for charges odd under <CPT symmetry>, states and their conjugates have equal thermal weights, so the equilibrium expectation of net <baryon number> vanishes and thermal stationarity prevents its sustained production. A nonequilibrium history allows different forward and reverse populations to generate an asymmetry. These are the standard necessary conditions for dynamical <baryogenesis> from symmetric initial conditions, not a guarantee of a sufficiently large asymmetry.
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