  We have attributed the elements from Sr through Ag in stars of low
metallicities ([Fe/H] < -1.5) to charged-particle reactions (CPR) in
neutrino-driven winds, which are associated with neutron star formation in
low-mass and normal supernovae (SNe) from progenitors of ~ 8 to 11 M_sun and ~
12 to 25 M_sun, respectively. Using this rule and attributing all Fe production
to normal SNe, we previously developed a phenomenological two-component model,
which predicts that [Sr/Fe] > -0.32 for all metal-poor stars. This is in direct
conflict with the high-resolution data now available, which show that there is
a great shortfall of Sr relative to Fe in many stars with [Fe/H] < -3. The same
conflict also exists for the CPR elements Y and Zr. We show that the data
require a stellar source leaving behind black holes and that hypernovae (HNe)
from progenitors of ~ 25 to 50 M_sun are the most plausible candidates. If we
expand our previous model to include three components (low-mass and normal SNe
and HNe), we find that essentially all of the data are very well described by
the new model. The HN yield pattern for the low-A elements from Na through Zn
(including Fe) is inferred from the stars deficient in Sr, Y, and Zr. We
estimate that HNe contributed ~ 24% of the bulk solar Fe inventory while normal
SNe contributed only ~ 9% (not the usually assumed ~ 33%). This implies a
greatly reduced role of normal SNe in the chemical evolution of the low-A
elements.
