The primary election as a means of choosing the states’ delegates to the national conventions where the presidential nominee is formally selected

a. was introduced during the Jacksonian era.

b. is used in Europe as well as in the United States.

c. has been adopted more widely in recent decades, such that the candidate who dominates the primaries can usually expect to have won enough delegates to be assured of nomination at the convention.

d. is designed to strengthen the political parties.

e. is being replaced by the open-caucus system of selecting delegates.