  We report Mo isotopic data for 16 15N-rich presolar SiC grains of type AB
(14N/15N<solar, AB1) and their correlated Sr and Ba isotope ratios when
available. Eight of the 16 AB1 grains show s-process Mo isotopic compositions,
together with s-process Ba and/or Sr isotopic compositions. We found that a
higher percentage of AB1 grains show anomalous isotopic compositions than that
of AB2 grains (14N/15N>solar), thus providing further support to the division
of the two AB subgroups recently proposed by Liu et al. (2017a), who showed
that AB1 grains most likely originated from Type II supernovae (SNe) with
explosive H burning. Comparison of the Sr, Mo, and Ba isotopic compositions of
the AB1 grains with SN model predictions indicates that the s-process isotopic
compositions of AB1 grains resulted from neutron-capture processes occurring
during the progenitor massive stars' pre-SN evolution rather than from an
explosive neutron-capture process. In addition, the observations of (1)
explosive H burning occurring in the C-rich regions of the progenitor SNe of SN
X grains as suggested by the isotopic compositions of X grains, and (2)
explosive H burning occurring both at the bottom of the He/C zone and at the
top of the He/N zone as suggested by model simulations, imply that explosive H
burning is a common phenomenon in outer SN zones.
