= Solution
For ordinary single <stars> in these old <globular clusters>, \b[no current <core-collapse supernovae> are expected, and no new <black holes> are expected from the normal plotted population]. Their <main-sequence turnoff> <masses> are typically around $0.8M_\odot$, far below the roughly $8M_\odot$ initial-<mass> scale for advanced burning and core collapse. More massive original <stars> exhausted their much shorter <main-sequence lifetimes> long ago. The precise transition <mass> depends on composition and mass loss, but this large separation makes the conclusion robust.
The low-<mass> <stars> now leaving the <main sequence> evolve through the <red giant branch>, helium ignition, <horizontal branch> and <Asymptotic giant branch>. They lose their envelopes and leave mainly carbon-oxygen <white dwarfs>, typically around $0.5$–$0.6M_\odot$ for current old-cluster progenitors, supported by <electron degeneracy pressure>. A visible <planetary nebula> is possible if the exposed core heats before the ejecta disperse; it is not guaranteed for every low-<mass> remnant. Lower-<mass> <main-sequence stars> repeat this evolution only much later, and the very lowest-<mass> isolated <stars> can ultimately leave helium-rich degenerate remnants without igniting helium.
The clusters may already contain <neutron stars> and <black holes> made by their original massive <stars>; these remnants need not appear on an optical <colour-magnitude diagram>. Binary interactions can instead produce stripped helium <white dwarfs>, mergers or a possible <Type Ia supernova>; such exceptions are distinct from normal single-<star> core collapse. No such special progenitor can be established from the damaged plots. In particular, a luminous <red giant> is not by itself evidence for a massive <core-collapse supernova> progenitor.
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