All of the following are current methods of selecting delegates to a major political party national convention except: . a. state presidential primaries. c. state conventions. b. state caucuses. d. selection by congress.

The selection of delegates that are elected to a major political party is carried out in different ways. One way is primary election where the selection is carried out by presidential primaries. Under the democratic republic,  selection is scheduled during state conventions or state caucuses. The answer here is D.

The congress completes the diagram