Final answer:
The social order not part of the early Roman Empire was the 'Optimates,' a political group from the late Republic, not a formal class.
Step-by-step explanation:
In the early empire, the social orders in Roman society were patricians, equites (equestrians), plebeians, and slaves. All of these categories enjoyed the status of citizenship except for slaves who were considered property and did not have any rights. Therefore, the correct answer is Slaves, as they were not a social order in the early empire.
The social order that was not a part of the early Roman Empire is Optimates (E). The Optimates were not a formal class but rather a political group in the late Roman Republic, consisting of the conservative senatorial majority interested in maintaining the status quo. The social classes that did exist in the early empire included the Patricians, Equestrians, Plebeians, and Slaves. Additionally, there were Freedmen, who were former slaves that had been released, and the Honestiores, a term that later referred to the more privileged class (not part of the early empire structure).