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
Cervical ripening is mainly due to the action of : 
Select and explain. 
A. PGE2, B. PGF2, C. PGI2, D. PGG7
A: PGE2
Answer: A: PGE2 
Explanation: PGE2