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': 'Clavicle is absent in: \nSelect and explain. \nA. Osteogenesis imperfecta, B. Cleidocranial dysostosis, C. Fibrous dysplasia, D. Osteopetrosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cleidocranial Dysplasia\n(Marie and Sainton’s disease, Scheuthauer-Marie-Sainton syndrome, mutational dysostosis).\nA congenital disorder of bone formation manifested with clavicular hypoplasia or agenesis with a narrow thorax, which allows approximation of the shoulders in front of the chest.', 'role': 'assistant'}]