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
Extension of knee joint is caused by 
Select and explain. 
A. Gracilis, B. Popliteus, C. Quadriceps femoris, D. Semitendinosus
C: Quadriceps femoris
Answer: C: Quadriceps femoris 
Explanation: C. i.e. Quadriceps femoris