How does Brutus’ tragic flaw of idealism contribute to his downfall?

A.) Brutus’ anger leads him to kill Caesar so that he can gain more power. His desire to rule Rome causes Octavius to kill Brutus.
B.) Brutus bases his decision to assassinate Caesar on what he believes is best for Rome. After killing Caesar, the Republic still falls apart, and Brutus eventually dies.
C.) Brutus’ shyness prevents him from standing up to Octavius’ army; this is the reason Brutus is killed.
D.) Brutus’ manipulative nature causes Cassius to turn against him; this is the reason Brutus is killed.