Correct Option: A

firm (Adjective) : fairly hard; not easy to press into a different shape; not likely to change
capricious (Adjective) : showing sudden changes in attitude or behaviour; unpredictable; changing suddenly and quickly; changeable
fickle (Adjective) : changing often and suddenly
indefinite (Adjective) : lasting for a period of time that has no fixed end; not clearly defined; imprecise
defiant (Adjective) : openly refusing to obey