This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': "Extreme widening of the periodontal ligament as seen in the radiograph is the characteristic feature of: \nSelect and explain. \nA. Scleroderma, B. Paget's disease, C. Pemphigus, D. All of the above", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Extreme widening of the periodontal ligament, two to four times the\xa0normal thickness has been reported originally by\xa0Stafne and Austin as characteristic\xa0of scleroderma.', 'role': 'assistant'}]