Why Did the Art of Rhetoric Enter into Decline Under

Why did the art of rhetoric enter into decline under the rule of Augustus?

A) Rhetorical skills no longer played a crucial role in politics, since the emperor's supremacy ruled out political debate in the public sphere.
B) Augustus altered the educational system so that rhetoric was no longer taught in schools.
C) Illiteracy rates rose drastically, as Roman expansion throughout the Mediterranean caused the number of slaves to swell.
D) Rome became so cosmopolitan and multicultural that many Roman subjects in the Augustan period could no longer understand Latin.