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 artery, B. Long saphenous vein, C. Tibialis anterior tendon, D. Peroneus tertius
A: Post tibial artery
Answer: A: Post tibial artery 
Explanation: From medial to lateral, structures passing under flexor retinaculum
-        Tibialis posterior
-        Flexor digitorum longus
-        Posterior tibial vessels
-        Tibial nerve
-        Flexor hallucis longus