A chronic injury is defined as having:

A chronic injury is typically characterized by a gradual onset and an extended duration. This means that the injury develops slowly over time, often as a result of repetitive stress or overuse, and persists for an extended period, potentially leading to ongoing problems if not addressed. The correct choice reflects this understanding, indicating that a chronic injury exhibits both a long onset and long duration, allowing for various symptoms to manifest gradually and persist over time.

In contrast, options involving short onset would suggest an acute injury or a sudden trauma, which does not align with the definition of chronic injuries. The focus in chronic injuries is on the prolonged nature of both the onset and duration, emphasizing that these injuries are often related to ongoing stressors or conditions rather than a single traumatic event.