At the Beginning of Each Presidential Election Year, a Number

At the beginning of each presidential election year, a number of candidates descend upon the sites of early contests because

A) a certain proportion of campaign money must be expended in each state in order to be eligible for federal matching funds.
B) the national committees of the two major parties require all candidates to participate in at least two-thirds of the state primaries.
C) candidates' names will be dropped from later primaries if they do not receive a minimum of 10 percent of the vote in each state.
D) it is important for a candidate to establish momentum by winning early primaries and caucuses.
E) none of the above