Final answer:
In a representative democracy, the most characteristic citizen action is voting for government leaders, as it is the primary method through which citizens exercise their power to elect officials who will represent their interests.
Step-by-step explanation:
In a representative democracy, citizen action encompasses various forms of participation that contribute to the democratic process. The characteristic feature of such a democracy involves citizens voting for government leaders. This is because, in a representative democracy, the public elects officials to represent their interests and make decisions on their behalf. Therefore, from the given options, B) Voting for government leaders best encapsulates a feature of a representative democracy. Other forms of participation like serving on a jury, though important to the civic process, are not exclusive to democracies and can exist in various systems of governance. Protesting against the government and asking for public opinion are also significant, but they do not define the representative aspect of the democracy as directly as voting does.