<em>"The Electoral College", </em>set out in Article II, Section 1 of the U.S. Constitution, allows states to have the same power of votes in spite of their number of population.
Due to that, a party could outcast the presidential candidate they don't want, even if such candidate was elected by the majority.
The parties nominate electors, usually by a central committee or the conventions; so when voters cast their ballot for President, they are actually voting for their <em>"State's Electors"</em>, who are not obliged to follow the results of the popular vote, thus sometimes <em>“faithless electors”</em> adversely choose a candidate they're not committed to.
A <em>"faithless elector</em><em>"</em> is simply a member of the "<em>Electoral College</em>" who votes against the party's candidate.
Thereby the answer is (B): <em>"It allows for faithless electors, or electors who do not vote according to the wishes of their states"</em>
