Which of the Following Is a Hypothesis to Explain the Origin

Which of the following is a hypothesis to explain the origin of the modern eukaryotic cell?

A) A cell evolved a nucleus first, then incorporated a proteobacterial cell that became a mitochondrion.
B) A cell evolved a nucleus first, then incorporated a cyanobacterial cell that became a mitochondrion.
C) A cyanobacterial cell became incorporated into an archaeon at the same time that eukaryotes developed.
D) A proteobacterial cell became incorporated into an archaeon at the same time that eukaryotes developed.
E) None of the answer options is correct.