Regarding the anatomical snuffbox, which of the following is true?: (A) Abductor pollicis longus forms the posterior wall, (B) Abductor pollicis longus and Extensor pollicis brevis form the anterior wall, (C) Basilica vein forms the roof, (D) Floor is formed by Extensor carpi radialis longus and brevis
Answer is B. Boundaries of anatomical snuff box :

Anterior / Lateral wall - Extensor pollicis brevis and abductor pollicis longus tendons. 
Posterior / medial wall - Extensor pollicis longus tendon.
Floor - Styloid process of radius, trapezium, scaphoid and base of first metacarpal.
Roof - Skin, fascia, starting of cephalic vein, superficial branch of radial nerve.
Content - radial artery.