This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lower limb, Subject name: Anatomy
Which of the following tendons passes below the sustentaculum Tali ? 
Select and explain. 
A. tibialis anterior, B. tibialis posterior, C. flexor digitorum longus, D. flexor hallucis longus
D: flexor hallucis longus
Answer: D: flexor hallucis longus 
Explanation: The attachments and relations of the medial surface of calcaneum as follows - The groove on the lower surface of the sustentaculum tali is occupied by the tendon of the flexor hallucis longus. The medial margin of the sustentaculum tali is related to the tendon of the flexor digitorum longus and provides attachment to: (a) the spring ligament anteriorly. (b) a slip from the tibialis posterior in the middle; (c) some of the superficial fibres of the deltoid ligament along the whole length; and (d) the medial talocalcanean ligament posteriorly. Below the groove for the flexor hallucis longus, the medial surface gives origin to the fleshy fibres of the medial head of the flexor digitorum accessorius. B D Chaurasia's Human Anatomy , seventh edition , volume 2 , pg. no.,36.