Asignificant difference between the social structure of the roman republic and the roman empire was that

1. the classes of the roman empire were more diverse than those of the roman republic

2. in the roman republic, freed people and slaves were two separate classes

3. there was a new upper class in the roman empire

4. in the roman empire, people had less opportunities to rise in social status

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).

the catholic church withhold people's access to the bible during the middle ages.

people could go to church and listen to the teachings, but it was absolutely forbidden to own and/or read the books of both the old and new testaments. it was also prohibited to translate the books (which where originally in biblical hebrew) to any other language.

this was done so the church could remain in control of what their teachings were and to enhance their importance and power, while also being able to judge people's actions through information that was unavailable for the general public.