The correct answer is A) Delegates vote to nominate a presidential candidate.
The activity that occurs at a party's national convention is "Delegates vote to nominate a presidential candidate."
The party's annual convention is the event that is organized every four years in which delegates nominate its candidate for the presidency of the United States. In the event, the delegates redefine the platform of the party. In the bipartisan system of the US, the Democratic Party and the Republican Party have shared power most of the time.
The other options of the question were B) Delegates vote to select the president and vice president. C) The remaining candidates hold one final televised debate. D) States decide whether to hold primary elections or caucuses.