Which of the Following Has NOT Been an Important Reason Why

Which of the following has NOT been an important reason why various military regimes have stepped down during the past 50 years?

A) The military had accomplished its major goals and saw no reason to stay on
B) Prospects for the economy looked bleak and the armed forces did not want to take the blame
C) Military rule has brought internal conflicts that had undermined military cohesion
D) Unpopular decisions by the military government had undermined the military's legitimacy as an institution
E) Disgruntled military officers had begun to defect and join opposition political parties