When the Parties Select Their Nominees for President

When the parties select their nominees for president

A) citizens vote for delegates at a national nominating convention, which then
Selects the candidate.
B) the party primaries and caucuses are purely for show, with the decision being made at the national convention by party leaders.
C) citizen votes do not really matter because of the Electoral College.
D) so-called superdelegates decide the nominee.