The correct answer is A. Rome's common people banded together, called themselves plebeians, and demanded political power.
The plebeians considered themselves Roman citizens; and had as such obligations (notably military service) and certain political rights. They were not a social class but the whole of citizenship.
Tradition attributes to king Servius Tullius (6th century BC) the inscription of the plebs in public records, organizing it into craft corporations (the collegia).
These reforms of Servio Tulio, based on the census, allowed the plebs to become part of the army and the centennial elections and, later, in the context of the struggles between patricians and commoners that characterized the first centuries of the Roman Republic, even of the same Senate, accessing all the magistracies.
The patrician-plebeian confrontations took place from the Secessio plebis of 494 BC until the promulgation of the Lex Hortensia in 287 BC.
Pressed by the demands of the plebs, the patricians consented to the drafting of a public and written legal code (Law of the Twelve Tables) that was successively amended and expanded with new laws granting commoners new rights (to marriage, to the priesthood, etc.), the ability to vote in the different Roman assemblies and the legal effectiveness of their resolutions (plebiscite), and the exclusive appointment of two magistrates (the tribunes of the plebs) with powers to guarantee their rights.