The correct answer is A.
A democracy is a political system based on civil rights. It is based in the principle of the social contract, which states how citizens hold the right to grant power to political representatives electing them through suffrage.
Political representatives organize themselves together with others with whom they share views, and this is how political parties are created. Party members participate in elections together, and will establish a goverment jointly if suceeding in the voting. Those political representatives grouped in parties are free to express their ideas in order to attract those voters who might feel identified with them.