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
Which of the following is TRUE regarding the level of the superficial palmar arch? 
Select and explain. 
A. Proximal border of extended thumb, B. Distal border of extended thumb, C. Proximal transverse palm crease, D. Distal transverse palm crease
B: Distal border of extended thumb
Answer: B: Distal border of extended thumb 
Explanation: The convexity of the superficial palmar arch is approximately at the level of a line drawn across the hand from the distal border of the extended thumb. The superficial palmar arch, which is the main termination of the ulnar aery, is completed on the radial side in a variable manner, e.g., by the radialis indicis.The arch lies on the flexor tendons and the branches of the median nerve, under cover of the palmar aponeurosis. It gives off several palmar digital aeries.