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: Gynaecology & Obstetrics
Marker for ovarian cancer is 
Select and explain. 
A. CA 125, B. Ca 19 - 19, C. Ca 15 - 5, D. Hypercalcemia
A: CA 125
Answer: A: CA 125 
Explanation: CA 125