The Differences in Voter Turnout in the United States ______

The differences in voter turnout in the United States ______.

A) are explained completely by individual differences in resources and psychological involvement
B) are explained completely by the institutional context in which elections are conducted
C) are explained by individual differences in resources as well as the institutional context of elections
D) have largely disappeared since the United States implemented a system of mandatory voting with the goal of improving policy outcomes