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
Which one of the following is longest acting IUCD: 
Select and explain. 
A. Progestase, B. Cu -- T -- 380, C. Mirena, D. Norgesterol
B: Cu -- T -- 380
Answer: B: Cu -- T -- 380 
Explanation: Cu -- T -- 380