Answer:
C: As an affirmation of her loyalty, Keysha agreed to become a secret agent.
Step-by-step explanation:
The revised sentence presented in the option C shows the change Alexander made to use the word affirmative as a noun, which is the word affirmation (the act of affirming; a statement or proposition that is declared to be true). In option A, affirmably is an adverb ; in B, affirm is a verb ; in D, affirmed is also a verb.