To Facilitate Collective Action, the Shape of Party Organization in the United

To facilitate collective action, the shape of party organization in the United States has followed which simple rule?

A) For every presidential election, a national committee will select a candidate.
B) For every district where an election is held, some kind of party unit should exist.
C) For every initiative by one political party, an equal but opposing initiative is promoted by the other political party.
D) For every candidate, the party must provide a vigorous campaign.