What can we learn from $B\to$ $\rho (\omega) K$ decays?

We show that in the PQCD approach the $B\to \rho(\omega) K$ decays display not only the dynamical penguin enhancement, the mechanism responsible for the large branching ratios (BRs) of $B\to \phi K$ decays, but also the importance of annihilation contributions. We find that the CP asymmetries (CPAs) of $B\to \rho^{\pm}K^{\mp}$, $B^{\mp}\to \rho^0(\omega)K^{\mp}$ (class I) are all over 50%.