The correct answers are C. treachery and E. perfidy.

The sentence is structured to present a common perception of Brutus, then counter it with a mitigating fact.
- The first part of the sentence, "Brutus is often held up as the embodiment of $\qquad$ ," refers to his act of deceiving and assassinating his friend, Julius Caesar. This act is universally considered a betrayal.
- The words treachery and perfidy both mean an act of deception or betrayal.
- The second part of the sentence, "yet, while it is true that he deceived his friend... one must not forget that Caesar had become both a danger to himself and the Republic," provides a counterargument to this simple label. This doesn't change the fact that the initial act was one of betrayal, but it explains his motivation, which is what the sentence is trying to convey.

The other options do not fit the context:
- A. wisdom and B. prudence are positive traits, which contradict the act of deceiving a friend.
- D. selflessness is also a positive trait. While one could argue Brutus's actions were selfless (for the good of the Republic), the initial deception is still an act of treachery.
- F. cowardice means a lack of courage. While his actions could be debated as cowardly, the core of the act is betrayal, not a lack of bravery.