Final answer:
Vulgarity corresponds with 'impropriety' due to its association with coarse, unrefined behavior or language that is socially unacceptable.
Step-by-step explanation:
The word "vulgarity" matches with option (a) impropriety. Vulgarity refers to the quality of being common, coarse, or unrefined in manner, which ties directly to the definition of impropriety, meaning a lack of proper manners or behavior. It is related to acting in a way that is socially unacceptable or offensive.
Examples of vulgarity include using crude language, making obscene gestures, or behaving in a manner that is considered disrespectful in a given culture.