Answer:
a) The codification of over 5000 Roman laws.
Step-by-step explanation:
In the 6th Century Byzantine ruler Justinian decided o codify all Roman laws, starting with the Twelve Tables. These Code became the foundation for the development of judiciary systems across the whole Europe. Therefore A is correct.
Option B and C have no connections whatsoever with the question itself.
Chinese laws haven't affected Byzantine Empire at all, while American laws were created much later, and are based on Anglo-Saxon judiciary system.