This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Extremity, Subject name: Anatomy
Medial boundary of the anatomical snuff box is formed by: 
Select and explain. 
A. Extensor pollicis Longus, B. Abductor pollicis longus, C. Extensor pollicis brevis, D. Abductor pollicis Brevis
A: Extensor pollicis Longus
Answer: A: Extensor pollicis Longus 
Explanation: Ans. A. Extensor pollicis LongusThe anatomical snuff box or snuffbox is a triangular deepening on the radial, dorsal aspect of the hand--at the level of the carpal bones, specifically, the scaphoid and trapezium bones forming the floor. The name originates from the use of this surface for placing and then sniffing powdered tobacco, or "snuff."Boundariesa. The medial border (ulnar side) of the snuffbox is the tendon of the extensor pollicis longus.b. The lateral border (radial side) is a pair of parallel and intimate tendons, of the extensor pollicis brevis and the abductor pollicis longus