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
Structure passing deep to flexor retinaculum is: 
Select and explain. 
A. Post tibial aery, B. Long saphenous vein, C. Tibialis ant. tendon, D. Peroneus teius
A: Post tibial aery
Answer: A: Post tibial aery 
Explanation: A. i.e. Posterior tibial aery