Which of the following is a verbal cue of aggressive behavior?

C is the correct answer because serious and directed swearing often serves as a clear verbal cue of aggressive behavior. This kind of language can indicate a person's heightened emotional state, displaying anger or hostility towards another individual. Verbal aggression, particularly when directed at someone, can escalate tensions in a situation, signaling that the individual is likely feeling threatened or provoked.

In contrast, other options like sudden movements and an increased breathing rate may indicate nervousness or excitement rather than direct aggression. While physical distance invasion can be a sign of aggression, it is primarily nonverbal and does not convey the same immediate emotional context as targeted swearing. Thus, swearing, particularly when serious and directed, is a vocal expression that directly reveals aggressive intent.