The pope in Rome and the patriarch in Constantinople argued about the treatment of heretics.
having icons in the church.
the language for church services.
the holy text

B, having icons in the church

I know this because I took a test with this same question!

This dispute was one of the many reasons that lead to a split between the 2, but it was also the root cause of the Iconoclast Controversy.

Hope this helps! :)

herodotus taught this. herodotus was an ancient greek historian who was born in halicarnassus in the persian empire. he is known for having written the book the histories, a detailed record of his "inquiry" on the origins of the greco-persian wars.