The Institutional Theory for Explaining the Persistence of the Two-Party

The institutional theory for explaining the persistence of the two-party system in America refers to

A) the fact that the two parties have each become societal landmarks.
B) the limited ability of voters to focus on more than two parties.
C) the American media's focus on only the two dominant parties.
D) America's heavy reliance on single-member districts for elections.
E) the two major parties are coalitions, drawing their support from large segments of the population.