Which of the following is a sign that indicates the possibility of an impacted tooth?

The presence of radiolucency on a radiograph is indicative of a potential tooth impaction because it suggests an area where bone has been altered or resorbed, often as a result of the pressure exerted by an impacted tooth. This radiolucency can represent a cyst, abnormality, or other underlying pathology associated with the tooth that is unable to erupt properly due to obstruction or lack of space in the dental arch. When a tooth is impacted, the surrounding structures may respond by exhibiting changes visible on X-rays. Thus, recognizing this sign on a radiograph can lead to a proper diagnosis and subsequent treatment planning for the impacted tooth.

In contrast, signs such as increased sensitivity to cold, localized swelling, and presence of pus may suggest other conditions such as inflammation, infection, or other dental pathologies, which do not directly indicate impaction but could be secondary effects resulting from an impaction or other dental issue.