The correct answer is “patricians and plebeians”.
The division of the social classes in Rome between Patricians and Plebeians was based on birth. Plebeians hold the political power in their hands, they were free citizens, they would be born on these influentional families and would always hold power and money.
The Plebeians were workers - farmers, builders, and others - they consisted of the majority of the population of Rome. It was possible to climb socially, but it was an almost impossible task since they had little money and almost no influence on politics.