Which of the following was not a factor that led to the fall of Rome? A. Corruption and decay of values.
B. Revolts led by slaves and lower classes.
C. Outside invaders like the Germanic (foreign) tribes.
D. Changes in society due to Christianity - i. e. more loyal to religion and less loyal to the empire.

Invasions by Barbarian tribes

The most straightforward theory for Western Rome's collapse pins the fall on a string of military losses sustained against outside forces. Rome had tangled with Germanic tribes for centuries, but by the 300s “barbarian” groups like the Goths had encroached beyond the Empire's borders.

Ibelieve it would be c