This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetus Placenta & Fetal Membrane, Subject name: Gynaecology & Obstetrics
[{'content': 'What is the pH of amniotic fluid? \nSelect and explain. \nA. 6.5-7, B. 7.1-7.3, C. 7.4-7.8, D. 7.8-8.1', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. 7.1-7.3Properties of amniotic fluid:a. pH:7.1-7.3b. Specific gravity: 1.010c. Osmolarity: 250mOsmol/l--a sign of fetal maturity.', 'role': 'assistant'}]