Denise is concerned about the poor performers in her gym. For example, last week one of the front desk clerks got into a heated argument with a client, who subsequently informed Denise that he was leaving the gyn$.$ Denise's first action when faced with unacceptable performance should be to:

Ignore the incident, since it probably won't happen again

Fire the employee

Place the employee on disciplinary leave

Warn the employee that this kind of behavior is unacceptable