Depends on what you're talking about. In fetus development?
Answer:
Harry breaks off his relationship with Fanny soon after he becomes acquainted with Anne.
You should choose whichever issue is most prominent, then research to find the topic with the most reliable information. from there, you can build your base on that solid information. it has to be facts or a legitimatized opinion, otherwise you can't easily defend your position on said topic. make sure your opinion is well founded. you should also be interested in the topic, otherwise your attention will slip.