Correct Answer: Courteous

Solution : The correct choice will be the first option.

Impolite: It means showing a lack of manners or disrespect; and not being polite.

Courteous: It denotes polite, respectful, and considerate in one's behaviour.

In this context, courteous is the antonym that represents the opposite behaviour of being impolite. 

The meanings of the other options are:

Superior: It denotes higher rank, status, or quality; in this context, it does not directly convey the opposite of impoliteness.

Uncivil: It means lacking in courtesy or politeness; rude or disrespectful; this is a more direct synonym of impolite.

Blunt: It means direct in speech, often to the point of being perceived as rude or lacking tact.

Therefore, the correct answer will be courteous.