  Nonfactorizable effects in hadronic charmless B -> PP, VP decays can be
parametrized in terms of the effective number of colors N_c in the effective
parameters $a_i^{eff}$ that are linear combinations of Wilson coefficients. It
is shown that N_c(V+A) in the penguin amplitudes induced by the (V-A)(V+A)
four-quark operators is different from N_c(V-A) in the decay amplitudes arising
from the (V-A)(V-A) operators. Central values of the branching ratios of
$B^\pm\to\omega \pi^\pm$ and $B\to\pi\pi$ decays favor $N_c(V-A)\approx 2$, in
accordance with the nonfactorizable effect observed in $B\to D^{(*)}\pi
(\rho)$. Measurements of the interference effects in $B^-\to\pi^-(\rho^-)\pi^0
(\rho^0)$ decays will provide a more decisive test on the parameter N_c(V-A).
However, $N_c(V+A)\sim 2$ is ruled out by $B^\pm\to\phi K^\pm$ and $B\to\phi
K^*$. We find that N_c(V+A) lies in the range $10\geq N_c(V+A)\geq 4.3$,
subject to the corrections from W-annihilation and space-like penguin effects.
With $N_c(V-A)\approx 2$ we show that the branching ratio of $B\to\eta' K$ is
enhanced considerably at small values of 1/N_c(V+A) so that it is compatible
with experiment. In particular, the measurement of $B^0\to\eta' K^0$ is now
well explained without resorting to any new mechanism or new physics beyond the
Standard Model. Finally, we point out that it is difficult to understand the
observed large branching ratio of $B^\pm\to\omega K^\pm$ within the present
framework. Inelastic final-state interactions may alleviate the difficulty with
this decay mode.
