A Researcher Discovers a New Microfossil

A researcher discovers a new microfossil. At first, he is uncertain whether this organism was a bacterium, archaeon, or protist. After careful study, he determines that this organism was a protist. What features were present in this microfossil that lead the researcher to this conclusion?

A) DNA survived in this microfossil over the millennia; its DNA sequence was likely similar to those present in certain modern-day protists.
B) This microfossil was of an organism that had a distinct endomembrane system (i.e., nuclear membrane, endoplasmic reticulum, etc.) .
C) The microfossil contained evidence of mitochondria and/or chloroplasts.
D) This microfossil contained morphologically complex cell walls.
E) All of these choices are correct.