Answer:
B. National conventions include speeches from party leaders and invited guests.
C. National parties adopt official platforms at conventions.
Step-by-step explanation:
B. National conventions include speeches from party leaders and invited guests.
C. National parties adopt official platforms at conventions.
These two elements of national party conventions are key because they are integral parts of the conventions. The speeches from party leaders and invited guests allow the party to share their message and vision with the public, while the adoption of official platforms allows the party to set their agenda and platform for the upcoming election.