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
Unlocking of knee joint is done by which muscle? 
Select and explain. 
A. Popliteus, B. Biceps femoris, C. Quadriceps, D. Gastrocnemeus
A: Popliteus
Answer: A: Popliteus 
Explanation: Ans. is 'a' i.e., Popliteus