Drawing a conclusion from the graph, the true statement from the option given is Voter turnout in national election years is irregular from 2006 to 2020.
Voter turnout in 2006 was 40% while in 2014 it was 35% `; hence, voters were more interested in 2006 than in 2014.
In some of the years given, less than 50% of Americans participated
Which means the true statement is "Voter turnout in national election years is irregular from 2006 to 2020"