Answer:
A.The empire was too large to keep united.
Explanation:
As the Roman Empire keep expanding, Romans developed a complex law system seeking the security of the people they came to conquest and in defending Roman citizens. Having the most powerful and coordinated army in the world, however, was always subject to the Barbaric threats: large groups of non-civilized peoples came in raids opening frontlines among the borders of the Roman Empire.
The Empire became unstable starting 300-500 CE with some internal divisions following the major split of Western and Eastern Roman Empires.
The split was meant to resist invasions from the Huns, and the Visigoths
Ultimately leading to the fall of the Western Roman Empire in 476 CE.
In 14AD Rome had been on the defensive, expelling Barbaric invasions that exhausted, in the end, the efforts to further expand the borders.
