SCURRILOUS:

The correct answer is C. Abusive.

Scurrilous means “offensively coarse or vulgar in language or behavior.” It is often used to describe speech or writing that is sexually explicit or that attacks someone in a personal way.

B. Ribald is similar to scurrilous, but it is more specifically used to describe speech or writing that is sexually suggestive or humorously vulgar.

A. Decent means “morally good or right.” It is not typically used to describe speech or writing.

D. Mitigate means “to make something less severe or intense.” It is not typically used to describe speech or writing.