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
[{'content': 'Easiest method of determining zygosity is : \nSelect and explain. \nA. Blood grouping, B. Sex of fetus, C. Placental examination, D. Amniotic fluid examination', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Placental examination', 'role': 'assistant'}]