Final answer:
Justinian was only able to achieve marginal success in enforcing religious uniformity and imposing Roman law. Therefore, the correct statement is that Justinian was only able to achieve marginal success.
Step-by-step explanation:
Justinian's goal was to enforce religious uniformity and impose Roman law on all his subject peoples. He saw Roman law as a way to unify the empire and sought to eradicate other forms of law. Justinian codified Roman law in the Corpus Juris Civilis, which influenced legal systems in Europe.
However, Justinian's wars were expensive, and after his death, Byzantium lost its reconquests in the west to Germanic invasions, and the Persians continued to pose a threat in the east.