Final answer:
Justinian's Code, formally called the Corpus Juris Civilis, simplified Roman laws, enabling citizens to understand and adhere to them, thus unifying the empire under Roman law.
Step-by-step explanation:
The code that simplified laws and allowed ordinary citizens the opportunity to understand and live by the laws of Roman society was C) Justinian's Code. This legal project, carried out by Emperor Justinian, compiled and edited Roman edicts issued from the second to the sixth century CE. Known formally as the Corpus Juris Civilis, it served as the foundation of many European legal systems that are still in use today, thereby enforcing Roman law throughout the empire and attempting to establish a sense of Roman unity.