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
The major contribution of the amniotic fluid after 20 weeks of gestation: 
Select and explain. 
A. Ultrafiltrate and maternal plasma, B. Fetal urine, C. Fetal lung fluid, D. Fetal skin
B: Fetal urine
Answer: B: Fetal urine 
Explanation: Origin of amniotic fluid: