I would go with hypothesis because I never heard any of the other answers in Bio and a hypothesis is an educated guess so it means what you already know and it’s an observation (I hope this helped!!)
Sister chromatids first appear during the S phase of the cell cycle.
Jdhcnejkckelcjfhdiwkxkxnjscj
A small cell lived inside a larger cell to the benefit of both cells.
Hope this helps!
