The members of the Board were impressed by the candidates urbane behaviour.

Answer: Option C

Urbane : (of a person, especially a man) courteous and refined in manner.
Rural : in, relating to, or characteristic of the countryside rather than the town.
Indifferent : having no particular interest or sympathy; unconcerned.
Rude : offensively impolite or bad-mannered.
Negative : consisting in or characterized by the absence rather than the presence of distinguishing features.

Antonym of Urbane is Rude