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': 'Distance between x-ray source and film cassette should be: \nSelect and explain. \nA. 60 inches, B. 50 inches, C. 65 Inches, D. 55 inches', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 3 distances\nx ray source – midsaggital \xa0: 5 Feet : 60” : 152.4 cm\nmid saggital – film cassettes \xa0: 15 cm Acc to Jacobson\n\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0 \xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0 18 cm = 7” = Gurkeerat sing\nx – ray source – film casetes : 176 ~ 170 cm\n\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0 around 66”', 'role': 'assistant'}]