  We consider the three principal LiBeB evolutionary models, CRI in which the
cosmic-ray source at all epochs of Galactic evolution is the average ISM,
CRI+LECR in which metal enriched low energy cosmic rays (LECRs) are
superimposed onto the CRI cosmic rays, and CRS in which the cosmic-ray source,
accelerated in superbubbles, is constant, independent of the ISM metallicity.
By considering the evolutionary trend of log(Be/H) vs. both [Fe/H] and [O/H],
we demonstrate that the CRI model is energetically untenable. We present
evolutionary trends for B-11/B-10 and B/Be which, combined with future
precision measurements, could distinguish between the CRS and CRI+LECR models.
We show that delayed LiBeB synthesis in the CRS model, due to the transport of
the cosmic rays, could explain why log(Be/H) is steeper vs. [O/H] than vs.
[Fe/H]. We also show that delayed deposition of Fe into star forming regions,
due to its incorporation into high velocity dust, could provide an explanation
for the possible rise of [O/Fe] with decreasing [Fe/H]. Observations of
refractory and volatile alpha-elements could test this scenario. There seems to
be a need for pregalactic or extragalactic Li-6 sources.
