This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Varicose Veins, Subject name: Surgery
Primary cause of varicose veins - 
Select and explain. 
A. Incompetent valve perforators, B. Intrinsic abnormality of venous wall, C. Venous hypertension, D. Decrease in collagen in venous wall
A: Incompetent valve perforators
Answer: A: Incompetent valve perforators 
Explanation: Ans. is A.