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': 'Thomas test detects \nSelect and explain. \nA. Shortening of lower limb, B. Flexion deformity of hip, C. Lengthening of lower limb, D. Intractness of tendoachillis tendon', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]