Which Piece of Evidence Best Supports the Endosymbiotic Theory of Organelle

Which piece of evidence best supports the endosymbiotic theory of organelle evolution?

A) The outer membrane of a mitochondrion and chloroplast resembles a eukaryotic cell while the inner membrane resembles that of a bacterial cell.
B) The inner membrane of a mitochondrion and chloroplast resembles a eukaryotic cell while the outer membrane resembles that of a bacterial cell.
C) Both mitochondria and chloroplasts divide by mitosis.
D) Mitochondria and chloroplasts are much larger than present day bacteria.