Answer:
The correct answer is D) Single-Member Districts
Step-by-step explanation:
The politics of the United States has long been dominated by two powerful parties that compete with one another. Today, the two parties that dominate US politics are the Republican party (also known as the GOP) and the democratic party.
Third-party or even independent candidates find it difficult to win elections since elected officials re selected through single-member districts.
During the 2016 elections, a third-party, the Libertarians did make some gains but did not even pose a minor threat to the dominance of democrats and republicans. This is why, Senator Bernie Sanders, who is an independent, Caucuses with the democrats.