  By employing the perturbative QCD (PQCD) factorization approach, we studied
the sixteen $B/B_s \to \eta_c (\pi, K, \eta^{(\prime)},\rho,K^*,\omega,\phi)$
decays with the inclusion of the currently known next-to-leading order (NLO)
contributions. We found the following main points: (a) for the five measured $B
\to \eta_c (K,K^*)$ and $B_s\to \eta_c\phi$ decays, the NLO contributions can
provide $ (80-180)\%$ enhancements to the leading order (LO) PQCD predictions
of their branching ratios, which play an important role to help us to interpret
the data; (b) for the seven ratios $R_{1,\cdots,7}$ of the branching ratios
defined among the properly selected pair of the considered decay modes, the
PQCD predictions for the values of $R_{3,4,5}$ agree well with those currently
available measurements from BaBar and Belle Collaboration; (c) for $B^0 \to
\eta_c K_S^0$ decay, the PQCD predictions for both the direct and mixing
induced CP asymmetries do agree very well with the measured values within
errors; and (d) the PQCD predictions for ratios $R_{1,2}$ and $R_{6,7}$ also
agree with the general expectations and will be tested by the future
experiments.
