The correct answer is D.
Direct democracy is exercised when voters, instead of electing political representatives that would govern and conduct policymaking on their behalf, are directly involved and can choose to support those policies that they consider to be more appropiate. Option D is the only situation in which the policy choice is directly made by citizens.
Options A, B or C cannot be correct because in all of them the decision-making is performed by a body or an institution constituted by representatives that have been elected by citizens: the Congress, the town hall or the President.
Nowadays, most democracies in the world are representative democracies were citizens whose representatives through suffrage, in opposition to direct democracies.
