Each item describes an observation of a hypothetical supernova. Classify each observation as either "Not surprising" if it fits in with our current understanding of supernovae, or "Surprising" if the observation would cause us to rethink our understanding of supernovae.
A. A white dwarf supernova in a galaxy of only old stars.
B. Two massive star supernovae occur in the same young star cluster.
C. A massive star supernova leaves behind no detectable compact object.
D. A massive star in a binary system explodes.
E. An isolated star like our Sun explodes as a white dwarf supernova.
F. A young (5 million years) star explodes as a white dwarf supernova.