Athenian democracy was so groundbreaking because it made politics the business of every male citizen, not just a few. Option C is correct.
During the 5th to 4th century BCEm Athens system of government was a democracy. Under this system, all male citizens had equal political rights, freedom of speech, and the opportunity to participate directly in the political sphere. Furthemore, citizens participate in a direct democracy whereby they themselves made the decisions by which they lived, and they actively served in the institutions that governed them as well, so that they directly controlled all parts of the political process.