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: Orthopaedics
[{'content': "Indicator (s) of poor prognosis in the pott's spine is/are -a)  Healed vertebral lesionb) Grade IV pott's spinec)  Kyphotic angle > 60°d)  Short duratione) Acute onset \nSelect and explain. \nA. ab, B. bc, C. abc, D. bcd", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]