Which of these empires had control over a large portion of the former Roman

The Byzantine Empire, known also as the Eastern Roman Empire, had control over a large portion of the former Roman Emperor, Including Constantinople, later known as Tsarigrad, nowadays known as Istanbul.

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.