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: Anatomy
[{'content': 'Extension of knee joint is caused by \nSelect and explain. \nA. Gracilis, B. Popliteus, C. Quadriceps femoris, D. Semitendinosus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C. i.e. Quadriceps femoris', 'role': 'assistant'}]