I believe that the correct answer is the third one: <em>arrogance</em>. The phrase <em>growing feathers</em> represents arrogant tone in the speaker.
Explanation:
When reading that particular line: "<em>These growing feathers plucked from Caesar's wing / Will make him fly an ordinary pitch,</em>" we can feel the arrogance in the tone of the speaker. Specially, when reading the word <em>plucked</em>, like the feathers were stolen from Caesar, like he feels proud of it. It represents an arrogant tone in FLAVIUS.
