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: ENT
[{'content': 'Rigid esophagoscopy is not done in -a) Cervical spine rigidity b) Aortic aneurysmc) Carcinoma esophagus d) Esophageal webe) Lung abscess \nSelect and explain. \nA. ac, B. ab, C. ad, D. bc', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Contraindications of esophagoscopy (rigid type):\n\nTrismus\nAneurysm of aorta\nReceding mandible\nAdvanced heart, liver, kidney diseases (relative contraindication).\nDiseases of cervical spine, e.g. cervical trauma, spondylitis, TB, osteophytes, kyphosis, etc.', 'role': 'assistant'}]