What is the strongest evidence for the idea that present-day eukaryotic aerobes are the descendants of the successful symbiotic association of anaerobes and aerobes?  

A) Mitochondria can produce ATP.
B) A mitochondrion can survive indefinitely when removed from a eukaryotic cell.
C) A mitochondrion has its own set of DNA molecules.
D) Fossilized mitochondria are older than the oldest fossilized eukaryotes.
E) All eukaryotic cells have mitochondria.