Grace Was Sitting in Class When, Without Warning, Her Heart

Grace was sitting in class when, without warning, her heart began to pound, her chest felt tight, and a feeling of dizziness came over her. She felt extremely fearful. Over the next few weeks, the same thing happened several times. Her doctor did not find anything wrong with her heart. Grace was probably suffering from

A) generalized anxiety disorder.
B) obsessive-compulsive disorder.
C) panic disorder.
D) social anxiety disorder.