Songs like that encouraged the people to join the army and fight for liberty and to take pride in their nation and be patriotic and similar things. This kind of music was very popular during that time, especially since the government supported it since the government needed people to fight in world war 1 and encouraged it heavily.
The voter participation measure shows how big was the turnout, that is, how many of the eligible voters actually voted in a community. The higher the turnout the higher degree of democracy in a country. It is measured because of noticing patterns and predicting future elections, especially when wanting to win an election since you can see who didn't vote and often find out why and change that.
The Answer I believe is C
C. Classical humanism and realistic paintings became popular.
The Renaissance was a time of great learning and growth, it especially popularized humanism which directly translated into the art of that time period. So A, B, and D are unlikely to bee the correct choices. Therefore, C is the correct answer.