This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Nonprogressive contraction of esophagus are: \nSelect and explain. \nA. Primary, B. Secondary, C. Tertiary, D. Quaternary', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) TertiaryRef: Sabiston 19th Edition, Page 1019* Primary and secondary peristalsis are normal* Tertiary peristalsis is abnormal', 'role': 'assistant'}]