It may be inferred from the passage that, in contrast to their present view, microbiologists once believed that
A． only a single feature of endospore biology was responsible for their success
B． potentially, a canning process could be developed that was capable of destroying all endospores
C． ultraviolet radiation was a possible means of destroying microorganisms that practice cellular dormancy
D． cellular mitosis was the root cause of the resilience of the microorganisms under discussion
E． only single-celled organisms, like those of fungal spores, could practice cellular dormancy