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
True about the anatomy of great saphenous vein- 
Select and explain. 
A. Starts as a continuation of medial marginal vein, B. Ends of femoral vein 2.5 cm below the inguinal ligament, C. There are 2-5 valves below the knee, D. Ascends 2.5-3 cm behind tibial malleolus
A: Starts as a continuation of medial marginal vein
Answer: A: Starts as a continuation of medial marginal vein 
Explanation: Great saphenous vein forms as continuation of medial marginal vein to which dorsal venous arch unites. It runs in front of medial malleolus and opens into femoral vein through the saphenous opening located at 4cms below and lateral to pubic tubercle. There are about 15-20 valves in the great saphenous vein.