All you have to do is basically as you said, drop the e in exposure and add -ure to the end.
Exposure
The correct answer of the given question above would be the last option. The author's choice of words affects the tone of the excerpt in a way that the words candor and legacy impart a complimentary tone. Candor means being open or honest. And these two words impart a flattering tone.
If there is a selection of answers I would go with
Repetition
Parallelism
maybe some others but I don't know all the poetic devices you have to chose from
