Which provides the voice of the nation's people?

The voice of the nation's people are usually the elected representatives. When we're electing people in a democratic country we're basically saying that these people are there to represent our interests. While it isn't always true that the people who get aelected also effectively represent our voice, it does happen though.

Well, since there is no provided option, the answer can be a public vote

It's where we can freely choose someone to represent us that will carry our voice in the government