  The Cabibbo allowed non-leptonic $B$-decays in two hadrons are studied,
within the factorization hypothesis, in the framework of Isgur and Wise theory
for the matrix elements of the $\Delta B=-\Delta C=\pm 1$ weak currents. The
$SU(2)_{HF}$ symmetry relates $|\Delta B|=1$ to $|\Delta C|=1$ currents, which
have been measured in the semileptonic strange decays of charmed particles. By
assuming colour screening and allowing for $SU(3)$ invariant contributions from
the annihilation terms with charmed final states one is able to comply with the
present experimental knowledge.\\ The $CP$ violating asymmetries in neutral $B$
decays are given for charmed final states in terms of the $K-M$ angles. With
the central values found for the annihilation parameters there is a destructive
(constructive) interference between the direct and annihilation terms in the
Cabibbo allowed (doubly forbidden) amplitudes for the decays into
$D^{0}(D^{*0})\pi^0$ and $D^0\rho^0$ so that they may be of the same order.
This would imply large asymmetries, for which however our present knowledge on
the amplitudes does not allow to predict even their sign.\\ We have better
confidence in our predictions for the charged final states than the neutral
ones and can draw the conclusion that the detection of the corresponding
asymmetries requires, at least, $10^6$ tagged neutral $B$-particles.
