What Is the Most Likely Way That a Presidential Candidate

What is the most likely way that a presidential candidate would win the presidency without winning a majority of the popular vote?

A) A third party candidate wins enough votes to deny any one candidate a majority.
B) There is an exact 50-50 tie between the top two candidates.
C) Many of the electors choose not to vote in protest of the electoral college.
D) Turnout is especially low for a presidential election.
E) Party conventions are unable to come up with a nominee in time for the election.