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: Dental
[{'content': 'The Broadbent - Bolton cephalometer was devised in: \nSelect and explain. \nA. 1930, B. 1927, C. 1931, D. 1946', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The value of radiography as a diagnostic aid in orthodontics was proclaimed by W.A. Price in 1990, 5\xa0years after the discovery of X-rays.\xa0\nThe method of radiographic cephalometry was later derived from\xa0long-established anthropologic craniometrics studies and the use of the Broadbent-Bolton cephalometer devised in 1931.\xa0\nThe head positioning cephalometer (more commonly referred to today\xa0as a cephalostat) allowed serial lateral skull radiographs to be obtained in a standardized manner, thus\xa0creating reproducible beam/ﬁlm/patient projection geometry.\xa0\nIn turn, this standardization of\xa0radiographic projections allowed the precise measurement and comparison of oral and craniofacial\xa0structures, either directly on the radiograph, or through the use of superimposed tracings of bony\xa0anatomic landmarks obtained from the radiograph.\n\n\xa0\nRef: Jacobson 3rd ed page no 139', 'role': 'assistant'}]