A. the resignation of a president
C. the assassination of a president
E. a president dying of natural causes while in office
The 25th amendment is the presidential succession in case something happens to the president. This is invoked if the president dies while in office, the vice presidency becomes vacant, if the president cannot fulfill their duties (ex. undergo a medical procedure that temporarily restraints them), or if congress finds the president to be an unfit leader and votes to remove them from office.