Which of the following is a sign of a more serious injury that should command immediate attention?

Persistent bleeding is a sign of a more serious injury that requires immediate attention. This condition indicates that there is significant injury to blood vessels, which can lead to considerable blood loss and potential shock if not addressed promptly. Blood loss can rapidly become life-threatening, necessitating immediate assessment and intervention to control the bleeding and stabilize the patient.

In contrast, localized swelling may indicate inflammation or injury but does not necessarily signify a critical condition. Minor redness can be a typical response to injury or irritation and usually does not indicate a severe problem. Occasional pain, while it can be distressing, may not correlate with a serious injury unless accompanied by additional concerning signs, such as swelling or persistent bleeding. Thus, the presence of persistent bleeding stands out as a critical situation needing swift medical action to prevent further complications.