What Was One of the Major Political Flaws of the Roman

What was one of the major political flaws of the Roman empire?

A) The balanced constitution was difficult to maintain in times of economic stress.
B) The absence of military authority made the empire vulnerable to attack from outside.
C) The emperors? authority was sharply limited by the consuls and tribunes, particularly in the area of legislation.
D) The emperors never established a clear line of succession, leaving decisions to the army.