The answer is D (direct democracy)
All citizens in Athens could participate directly in the government. This form of government is called a direct democracy because each person's decision directly affects the outcome of a vote.
In Athens, citizens gathered together to discuss issues and vote on them. Each person's vote counted and the majority ruled.
In a true direct democracy, every single law, bill or issue of justice is voted on by all the people. A direct democracy is usually contrasted with a representative democracy where the general public votes for representatives, who then make laws on its behalf.