A Teenage Girl Had Been Feeling Depressed and Having Panic

A teenage girl had been feeling depressed and having panic attacks.Her doctor prescribed medication.She was sitting in her room feeling very depressed, so to cheer her up, a friend suggested that they go to an exercise class.Shortly after the warm-up started, she had another panic attack.What is the best explanation for this occurrence?

A) She was angry with the friend for insisting that she go out.
B) The physical sensations experienced during exercise had become an internal cue for panic to occur.
C) The medication that had been prescribed for her was treating only the depression not the anxiety.
D) The exercise class was an unconditioned stimulus that resulted in a panic attack.