The Romans overthrew rule by the Etruscans during the Roman-Estruscan Wars. This victory was monumental in the formulation of the Roman Republic. The Etruscans supported the deposed king Lucius Tarquinus Superbus with a military showing, but were thoroughly defeated by Roman Republic forces at the Battle of Silva Arsia. The other answers are incorrect because these groups posed threats at later times in Roman history.

Plebeian tribunes were the primary representation of the common people of Rome in the government of the Roman Republic. Plebeian tribunes were appointed to represent the interests of the plebeian class and wielded a considerable amount of political power, particularly towards the end of the history of the Roman Republic. The most significant, and first, political power of the plebeian tribunes was the ability to veto decisions made by consuls and magistrates. This was a significant check that the plebeians had on the power of the patricians.

Consuls were the highest elected officials in the Roman Republic. Two consuls were appointed at one time to serve concurrently for terms of one year. They had numerous responsibilities, including leading the armies of the Roman Republic in times of war. They were more likely to be patricians (noblemen) than plebeians. They did not, however, generally have dictatorial levels of power. Rome sometimes did require temporary dictators, in times of war or chaos, but these dictators were distinct from consuls.

The Tribune of the Plebs was created in the early years of the Roman Republic, around 495 BCE. It was the result of class tensions between the ruling patricians and the relatively powerless plebeians. These class tensions would continue for at least another two centuries (and essentially throughout the entire history of the Roman Republic), but the Tribune of the Plebs was in existence for almost all of these struggles. The Tribune of the Plebs was capable of taking legislative action, but initially only the plebeians were obligated to follow these “plebiscites.”

Tiberius and Gaius Gracchus were brothers who served as plebeian tribunes in the second century BCE. They were both populares, which means they achieved political power through the support of the common people and the assemblies. They are both remembered for their attempts to improve the lives of poor plebeians in the Roman Republic. Tiberius tried to accomplish this by taking land away from the richest members of society and redistributing it to the poor. Gaius went even further than his brother in his attempted reforms, but his actions eventually led to the outbreak of the Social War and civil war in the Roman Republic.

The Conflict of Orders is the name given to a prolonged class struggle between the "patricians" (aristocrats) and plebeians (common people) in the Roman Republic. It began in the early years of the Roman Republic when the plebeians, feeling excluded from the political process and persecuted, rebelled against the authority of the patricians. Over a period of time lasting more than a century, the plebeians would slowly gain more and more rights for themselves and eventually gained access to political participation and government.

The Centuriate Assembly was one of the governing bodies of the Roman Republic. The Centuriate Assembly is so named because it divided the Roman population into one hundred groups, each with their own representative in the assembly. The Centuriate Assembly was the most powerful assembly for most of the history of the Roman Republic. The Centuriate Assembly was responsible for declaring war and was the only governing body which could elect magistrates like praetors, consuls, and quaestors.

The Tribal Assembly was one of the democratic governing bodies of the Roman Republic. It was comprised of a small number of urban “tribes” and a large number of rural “tribes.” These “tribes” were groups of citizens organized on the basis of where they lived. The Tribal Assembly had the power to vote on certain legislative issues, appoint lower ranking magistrates, and try certain judicial cases.

A plebiscite was a law enacted by the Council of Plebeians in the Roman Republic. Generally, the law applied only to common people — the plebeians — and was not applicable to the aristocratic class, the patricians.

Magistrates were elected or appointed officials in the Roman Republic, who were chosen to carry out specific functions of the Roman government. Examples of magistrates in the Roman Republic include censors, quaestors, praetors, aediles, and consuls.