One Stabilizing Factor in the Reigns of the Golden Age

One stabilizing factor in the reigns of the Golden Age emperors was that the first four emperors

A) had no surviving sons and were therefore able to use adoption to find the best possible successor.
B) engaged in shrewd public relations by stamping their images on coins, establishing their imperial cults, and inscribing their names on public buildings.
C) generously paid an enormous number of soldiers who collected taxes and maintained peace at all costs.
D) offered to all their loyal subjects the possibility and attendant rewards of citizenship, regardless of gender, nationality, or ethnicity.