Since 1952, Democrats Have Generally Been a Majority of the Electorate

Since 1952, Democrats have generally been a majority of the electorate, but Republicans have won more presidential elections for which of the following reasons?

A) Polls estimating the Democrat voter population are faulty.
B) Republican Party identification has changed over the years.
C) Democrats are more likely to "defect" on the basis of candidates' attributes and the issues.
D) Democrats have failed to field candidates in some elections.
E) Voters are disenchanted with the Democrats' perennial fundraising advantage over Republicans.