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
Tumor marker most helpful in follow up of a case of Epithelial carcinoma of ovary is : 
Select and explain. 
A. CA - 125, B. Serum Alpha Fetoprotein, C. Serum human chorionic gonadotropin, D. Human Placental Lactogen
A: CA - 125
Answer: A: CA - 125 
Explanation: CA - 125