The correct answers are B) multiple civil wars, D) economic collapse due to inflation, and E) repeated invasions from all over.
The three things that brought about the fall of Rome when they all hit at once were the multiple civil wars, economic collapse due to inflation, and repeated invasions from all over.
Historians such as Edward Gibbon consider that the fall of the Roman Empire started in 476 CE when Germans deposed Romulus Augustus form the Western part of the empire. Among the reasons for the decline of the Roman Empire, historians consider the rise of Islam, the rise of Christianity, the tremendous expansion that not allowed for proper control of the territories, multiple civil wars, economic collapse due to inflation, and repeated invasions from all over.