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: Unknown
Mc benign epithelial ovarian tumor is 
Select and explain. 
A. Serous cystadenoma, B. Mucinous cystadenoma, C. Brenner tumor, D. Ovarian fibroma
A: Serous cystadenoma
Answer: A: Serous cystadenoma 
Explanation: Serous cystadenoma and cystadenocarcinoma
Serous cystadenoma and cystadenocarcinoma are amongst the most common of cystic ovarian neoplasms, accounting about 50% of all ovarian tumours; of these, 60-70% are benign, 15% borderline and 20-25% are malignant.