Political parties meet at to select their presidential and vice presidential nominees.

The correct answer is conventions.

Every four years, members of the Democratic and Republican parties meet at conventions to announce who their candidates will be for president and vice president. The selection of these candidates are based on the results of the primaries and caucuses held during the winter months. Then, in the summer, the parties meet at their respective conventions to announce their nominees.

  the domino theory states that  if one country in a region came under the influence of communism, then the surrounding countries would follow in a  domino  effect.

The mercantilism option