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
Progestase is effective for : 
Select and explain. 
A. 1 year, B. 2 years, C. 4 years, D. 5 years
A: 1 year
Answer: A: 1 year 
Explanation: 1 year