Which of the following is an internal stressor?

An internal stressor refers to stress that originates from within an individual, often related to emotions, thoughts, or personal experiences. In this case, fear of medical test results exemplifies an internal stressor because it arises from the individual's own perception and emotional response to a specific situation. This fear can manifest due to anxiety or concern about health outcomes, illustrating how internal thoughts and feelings can create stress.

The other options represent external stressors. Financial problems are situational issues that affect a person's circumstances but originate outside of individual thoughts or emotions. Relationship issues involve interactions with others and the complexities of human relationships, while work deadlines are external pressures related to job responsibilities and time constraints. Each of these stressors can certainly contribute to stress experiences, but they do not stem from personal, internal emotional processes in the same way as the fear of medical test results does.