  We use a recently developed model of relativistic meson-exchange currents to
compute the neutron-proton and proton-proton yields in $(\nu_\mu,\mu^-)$
scattering from $^{12}$C in the 2p-2h channel. We compute the response
functions and cross sections with the relativistic Fermi gas model for
different kinematics from intermediate to high momentum transfers. We find a
large contribution of neutron-proton configurations in the initial state, as
compared to proton-proton pairs. In the case of charge-changing neutrino
scattering the 2p-2h cross section of proton-proton emission ({\it i.e.,} np in
the initial state) is much larger than for neutron-proton emission ({\it i.e.,}
two neutrons in the initial state) by a $(\omega,q)$-dependent factor. The
different emission probabilities of distinct species of nucleon pairs are
produced in our model only by meson-exchange currents, mainly by the $\Delta$
isobar current. We also analyze other effects including exchange contributions
and the effect of the axial and vector currents.
