Answer :

Rome was a republic before it was an empire. Romans had the first Senate, elected by the people. The third option is also correct, because even the if the emperor did something that was against the law, he would be put on trial. Also the last one, those are called "Law's" You find them everywhere. xD  Hope I helped :)

The correct answer of this question is the idea of representative government in which people elect officials to speak for them. It is possible through the process of voting. Of course, with the first proposed law system and as one of the first nations where fundamentals of democracy attained, concept of individual rights was also coming from Rome.