The correct answer is Buddhism and central government.
A linguist studies language in a scientific way; so not just a certain language like Spanish, Mandarin or such, but how a language is written, communicated, it's forms, etc.
The byzantine empire lost Rome. Rome was claimed by the byzantines in the 6th century and in the 6th century was given to the papacy as the major seat and capitol of the papal state
Poor growing conditions, droughts, disease, Native Americans, less profit because it costed more to transport crops.
They both helped keep the balance between free and slave states .