Final answer:
The Schachter-Singer two-factor theory of emotion best explains Conrad's chain of events.
Step-by-step explanation:
The chain of events described in the scenario can be best explained by the Schachter-Singer two-factor theory of emotion. According to this theory, emotions are composed of two factors: physiological arousal and cognitive appraisal. In this case, Conrad's physiological arousal from studying intensively for finals and then experiencing the flu symptoms after the exams could have influenced his cognitive appraisal and led to a negative emotional experience.