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: Pathology
Which of the following is most common type of ovarian tumors? 
Select and explain. 
A. Granulosal cell tumor, B. Serous epithelial tumor, C. Mature teratoma, D. Dysgerminoma
B: Serous epithelial tumor
Answer: B: Serous epithelial tumor 
Explanation: Serous epithelial tumor are the most common type of ovarian tumors.