Final answer:
The key feature of Somatization Symptom Disorder is frequent and diverse physical complaints with no medical explanation. Patients with this condition experience significant distress from these symptoms, which cannot be fully explained by a medical condition or another mental disorder.
Step-by-step explanation:
The key feature of Somatization Symptom Disorder, previously known as Briquet's Syndrome, is B) Frequent and diverse physical complaints with no medical explanation. This condition is characterized by a pattern of recurring, clinically significant complaints about physical symptoms that cannot be fully explained by a medical condition, substance use, or another mental disorder. Patients with Somatization Symptom Disorder experience significant distress and impairment in social, occupational, or other areas of functioning due to their preoccupation with these symptoms.
In contrast to Somatization Symptom Disorder, each of the other options in the student's question refers to different conditions. Option A) Excessive worry about physical appearance is often related to disorders such as Body Dysmorphic Disorder and can also be a feature of anorexia nervosa. Option C) Intense fear of gaining weight, leading to extreme dieting is descriptive of anorexia nervosa. Lastly, option D) describes symptoms that might be part of neurological conditions such as Parkinson's disease or other disorders affecting motor function, but it does not accurately describe Somatization Symptom Disorder.