A 27- year- old man presents to a psychiatrist for evaluation of anxiety. He explains that he recently got a promotion at his job, which requires frequent traveling. Although he is excited about his new role, he is terrified about the prospect of flying. He describes that the last time he flew, 5 years ago, he felt extremely anxious, with rapid heart rate, rapid breathing, nausea, and tingling in his hands. He was terrified that the plane would crash and he would die. He has avoided flying ever since, but he can also feel extremely anxious to the point of hyperventilating when even a discussion of flying comes up. Now he has a business trip in 3 weeks and he is "mortified". He is considering whether to ask for a demotion. He denies feeling anxious in any other situations. What is the likely diagnosis?

A. Generalized anxiety disorder.
B. Panic disorder.
C. Simple phobia.
D. Social anxiety disorder.