It is Big Bang and cannot be proved. A hypotheses must be testable. Big Bang is not testable.
I found the attached image on the internet related to this question.
The solid arrows represent neuronal communication. The stimulus, the effects, and the flow of information is all done by receptors and synapses that send a signals across the body in order to have effective feedback responses promoting the homeostasis of the organism.
Use a sandbag to hold it in place
During the S phase in the cell cycle, the chromosomes are replicated so that there are two copies. These copies are necessary so that each daughter cell created during the M phase will have an identical copy of the DNA.
Therefore, the answer is A: The DNA must be replicated.
The chromosomes joining, cell membrane expanding, and cytoplasm separating all happen during the M phase (mitosis).