Answer :
Well, since we know an antonym is the opposite, and patronize means to treat someone kindly, we can choose C. scornful. :)
I would go with c. Here is a list of synonyms and other antonyms:
Synonyms: Deign, Snub, Favor, Indulge, Stoop, Be gracious to, and to be lofty
Antonyms: Oppose, Contend, Ignore, Hurt, and Antagonize
I really hope this helps you!!!:P