A 41- year- old man reports to the psychiatrist that he is afraid of dentists. He has a hx of extreme anxiety upon entering a dental office, to the point that he feels dizzy and nauseated. He becomes excessively anxious in the waiting room and has a very difficult time completing visits. He is so fearful about dentists that he reports he cannot take his own children to their dentist b/c he has "anxiety attacks" in the office. Rather, he insists that his wife take the children. His aversion to the dentists has led to his missing regular appointments for more than 6 years. He plans to go soon, only b/c he has severe tooth pain and believes he may need a root canal. He does not have anxiety in other contexts. What is the likely diagnosis?

A. Adjustment disorder with anxiety.
B. Generalized anxiety disorder.
C. Posttraumatic stress disorder.
D. Specific phobia.