Some scientists think that complex eukaryotic cells formed from the union of two separate prokaryotic cells. The engulfing of one prokaryotic cell by another is a plausible explanation of why
a
organelles in a eukaryotic cell work cooperatively.
b
eukaryotic cells lack the defense mechanisms of prokaryotic cells.
c
eukaryotic cells don't share any similarities with prokaryotic cells.
d
organelles in a eukaryotic cell would attack other cells.