Final answer:
The reduction in the patient's fear is best understood in terms of c)the two-factor theory of emotion, which states that emotions are composed of physiological arousal and cognitive interpretation.
Step-by-step explanation:
The reduction in the patient's fear can be best understood in terms of the two-factor theory of emotion. According to this theory, emotions are composed of two factors: physiological arousal and cognitive interpretation. In the given scenario, the therapist reframes the patient's rapid breathing as a natural consequence of too little oxygen in a small enclosed space, unrelated to fear. This cognitive reinterpretation of the patient's arousal leads to a reduction in fear. The two-factor theory suggests that our interpretation of physiological arousal influences our emotional experience.